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| Type | Label | Description |
|---|---|---|
| Statement | ||
| Theorem | fsuppssindlem1 42601* | Lemma for fsuppssind 42603. Functions are zero outside of their support. (Contributed by SN, 15-Jul-2024.) |
| ⊢ (𝜑 → 0 ∈ 𝑊) & ⊢ (𝜑 → 𝐼 ∈ 𝑉) & ⊢ (𝜑 → 𝐹:𝐼⟶𝐵) & ⊢ (𝜑 → (𝐹 supp 0 ) ⊆ 𝑆) ⇒ ⊢ (𝜑 → 𝐹 = (𝑥 ∈ 𝐼 ↦ if(𝑥 ∈ 𝑆, ((𝐹 ↾ 𝑆)‘𝑥), 0 ))) | ||
| Theorem | fsuppssindlem2 42602* | Lemma for fsuppssind 42603. Write a function as a union. (Contributed by SN, 15-Jul-2024.) |
| ⊢ (𝜑 → 𝐵 ∈ 𝑊) & ⊢ (𝜑 → 𝐼 ∈ 𝑉) & ⊢ (𝜑 → 𝑆 ⊆ 𝐼) ⇒ ⊢ (𝜑 → (𝐹 ∈ {𝑓 ∈ (𝐵 ↑m 𝑆) ∣ (𝑥 ∈ 𝐼 ↦ if(𝑥 ∈ 𝑆, (𝑓‘𝑥), 0 )) ∈ 𝐻} ↔ (𝐹:𝑆⟶𝐵 ∧ (𝐹 ∪ ((𝐼 ∖ 𝑆) × { 0 })) ∈ 𝐻))) | ||
| Theorem | fsuppssind 42603* | Induction on functions 𝐹:𝐴⟶𝐵 with finite support (see fsuppind 42600) whose supports are subsets of 𝑆. (Contributed by SN, 15-Jun-2024.) |
| ⊢ 𝐵 = (Base‘𝐺) & ⊢ 0 = (0g‘𝐺) & ⊢ + = (+g‘𝐺) & ⊢ (𝜑 → 𝐺 ∈ Grp) & ⊢ (𝜑 → 𝐼 ∈ 𝑉) & ⊢ (𝜑 → 𝑆 ⊆ 𝐼) & ⊢ (𝜑 → (𝐼 × { 0 }) ∈ 𝐻) & ⊢ ((𝜑 ∧ (𝑎 ∈ 𝑆 ∧ 𝑏 ∈ 𝐵)) → (𝑠 ∈ 𝐼 ↦ if(𝑠 = 𝑎, 𝑏, 0 )) ∈ 𝐻) & ⊢ ((𝜑 ∧ (𝑥 ∈ 𝐻 ∧ 𝑦 ∈ 𝐻)) → (𝑥 ∘f + 𝑦) ∈ 𝐻) & ⊢ (𝜑 → 𝑋:𝐼⟶𝐵) & ⊢ (𝜑 → 𝑋 finSupp 0 ) & ⊢ (𝜑 → (𝑋 supp 0 ) ⊆ 𝑆) ⇒ ⊢ (𝜑 → 𝑋 ∈ 𝐻) | ||
| Theorem | mhpind 42604* | The homogeneous polynomials of degree 𝑁 are generated by the terms of degree 𝑁 and addition. (Contributed by SN, 28-Jul-2024.) |
| ⊢ 𝐻 = (𝐼 mHomP 𝑅) & ⊢ 𝐵 = (Base‘𝑅) & ⊢ 0 = (0g‘𝑅) & ⊢ 𝑃 = (𝐼 mPoly 𝑅) & ⊢ + = (+g‘𝑃) & ⊢ 𝐷 = {ℎ ∈ (ℕ0 ↑m 𝐼) ∣ (◡ℎ “ ℕ) ∈ Fin} & ⊢ 𝑆 = {𝑔 ∈ 𝐷 ∣ ((ℂfld ↾s ℕ0) Σg 𝑔) = 𝑁} & ⊢ (𝜑 → 𝑅 ∈ Grp) & ⊢ (𝜑 → 𝑋 ∈ (𝐻‘𝑁)) & ⊢ (𝜑 → (𝐷 × { 0 }) ∈ 𝐺) & ⊢ ((𝜑 ∧ (𝑎 ∈ 𝑆 ∧ 𝑏 ∈ 𝐵)) → (𝑠 ∈ 𝐷 ↦ if(𝑠 = 𝑎, 𝑏, 0 )) ∈ 𝐺) & ⊢ ((𝜑 ∧ (𝑥 ∈ ((𝐻‘𝑁) ∩ 𝐺) ∧ 𝑦 ∈ ((𝐻‘𝑁) ∩ 𝐺))) → (𝑥 + 𝑦) ∈ 𝐺) ⇒ ⊢ (𝜑 → 𝑋 ∈ 𝐺) | ||
| Theorem | evlsmhpvvval 42605* | Give a formula for the evaluation of a homogeneous polynomial given assignments from variables to values. The difference between this and evlsvvval 42573 is that 𝑏 ∈ 𝐷 is restricted to 𝑏 ∈ 𝐺, that is, we can evaluate an 𝑁-th degree homogeneous polynomial over just the terms where the sum of all variable degrees is 𝑁. (Contributed by SN, 5-Mar-2025.) |
| ⊢ 𝑄 = ((𝐼 evalSub 𝑆)‘𝑅) & ⊢ 𝐻 = (𝐼 mHomP 𝑈) & ⊢ 𝑈 = (𝑆 ↾s 𝑅) & ⊢ 𝐷 = {ℎ ∈ (ℕ0 ↑m 𝐼) ∣ (◡ℎ “ ℕ) ∈ Fin} & ⊢ 𝐺 = {𝑔 ∈ 𝐷 ∣ ((ℂfld ↾s ℕ0) Σg 𝑔) = 𝑁} & ⊢ 𝐾 = (Base‘𝑆) & ⊢ 𝑀 = (mulGrp‘𝑆) & ⊢ ↑ = (.g‘𝑀) & ⊢ · = (.r‘𝑆) & ⊢ (𝜑 → 𝑆 ∈ CRing) & ⊢ (𝜑 → 𝑅 ∈ (SubRing‘𝑆)) & ⊢ (𝜑 → 𝐹 ∈ (𝐻‘𝑁)) & ⊢ (𝜑 → 𝐴 ∈ (𝐾 ↑m 𝐼)) ⇒ ⊢ (𝜑 → ((𝑄‘𝐹)‘𝐴) = (𝑆 Σg (𝑏 ∈ 𝐺 ↦ ((𝐹‘𝑏) · (𝑀 Σg (𝑖 ∈ 𝐼 ↦ ((𝑏‘𝑖) ↑ (𝐴‘𝑖)))))))) | ||
| Theorem | mhphflem 42606* | Lemma for mhphf 42607. Add several multiples of 𝐿 together, in a case where the total amount of multiplies is 𝑁. (Contributed by SN, 30-Jul-2024.) |
| ⊢ 𝐷 = {ℎ ∈ (ℕ0 ↑m 𝐼) ∣ (◡ℎ “ ℕ) ∈ Fin} & ⊢ 𝐻 = {𝑔 ∈ 𝐷 ∣ ((ℂfld ↾s ℕ0) Σg 𝑔) = 𝑁} & ⊢ 𝐵 = (Base‘𝐺) & ⊢ · = (.g‘𝐺) & ⊢ (𝜑 → 𝐼 ∈ 𝑉) & ⊢ (𝜑 → 𝐺 ∈ Mnd) & ⊢ (𝜑 → 𝐿 ∈ 𝐵) & ⊢ (𝜑 → 𝑁 ∈ ℕ0) ⇒ ⊢ ((𝜑 ∧ 𝑎 ∈ 𝐻) → (𝐺 Σg (𝑣 ∈ 𝐼 ↦ ((𝑎‘𝑣) · 𝐿))) = (𝑁 · 𝐿)) | ||
| Theorem | mhphf 42607 | A homogeneous polynomial defines a homogeneous function. Equivalently, an algebraic form is a homogeneous function. (An algebraic form is the function corresponding to a homogeneous polynomial, which in this case is the (𝑄‘𝑋) which corresponds to 𝑋). (Contributed by SN, 28-Jul-2024.) (Proof shortened by SN, 8-Mar-2025.) |
| ⊢ 𝑄 = ((𝐼 evalSub 𝑆)‘𝑅) & ⊢ 𝐻 = (𝐼 mHomP 𝑈) & ⊢ 𝑈 = (𝑆 ↾s 𝑅) & ⊢ 𝐾 = (Base‘𝑆) & ⊢ · = (.r‘𝑆) & ⊢ ↑ = (.g‘(mulGrp‘𝑆)) & ⊢ (𝜑 → 𝑆 ∈ CRing) & ⊢ (𝜑 → 𝑅 ∈ (SubRing‘𝑆)) & ⊢ (𝜑 → 𝐿 ∈ 𝑅) & ⊢ (𝜑 → 𝑋 ∈ (𝐻‘𝑁)) & ⊢ (𝜑 → 𝐴 ∈ (𝐾 ↑m 𝐼)) ⇒ ⊢ (𝜑 → ((𝑄‘𝑋)‘((𝐼 × {𝐿}) ∘f · 𝐴)) = ((𝑁 ↑ 𝐿) · ((𝑄‘𝑋)‘𝐴))) | ||
| Theorem | mhphf2 42608 |
A homogeneous polynomial defines a homogeneous function; this is mhphf 42607
with simpler notation in the conclusion in exchange for a complex
definition of ∙, which is
based on frlmvscafval 21786 but without the
finite support restriction (frlmpws 21770, frlmbas 21775) on the assignments
𝐴 from variables to values.
TODO?: Polynomials (df-mpl 21931) are defined to have a finite amount of terms (of finite degree). As such, any assignment may be replaced by an assignment with finite support (as only a finite amount of variables matter in a given polynomial, even if the set of variables is infinite). So the finite support restriction can be assumed without loss of generality. (Contributed by SN, 11-Nov-2024.) |
| ⊢ 𝑄 = ((𝐼 evalSub 𝑆)‘𝑅) & ⊢ 𝐻 = (𝐼 mHomP 𝑈) & ⊢ 𝑈 = (𝑆 ↾s 𝑅) & ⊢ 𝐾 = (Base‘𝑆) & ⊢ ∙ = ( ·𝑠 ‘((ringLMod‘𝑆) ↑s 𝐼)) & ⊢ · = (.r‘𝑆) & ⊢ ↑ = (.g‘(mulGrp‘𝑆)) & ⊢ (𝜑 → 𝑆 ∈ CRing) & ⊢ (𝜑 → 𝑅 ∈ (SubRing‘𝑆)) & ⊢ (𝜑 → 𝐿 ∈ 𝑅) & ⊢ (𝜑 → 𝑋 ∈ (𝐻‘𝑁)) & ⊢ (𝜑 → 𝐴 ∈ (𝐾 ↑m 𝐼)) ⇒ ⊢ (𝜑 → ((𝑄‘𝑋)‘(𝐿 ∙ 𝐴)) = ((𝑁 ↑ 𝐿) · ((𝑄‘𝑋)‘𝐴))) | ||
| Theorem | mhphf3 42609 | A homogeneous polynomial defines a homogeneous function; this is mhphf2 42608 with the finite support restriction (frlmpws 21770, frlmbas 21775) on the assignments 𝐴 from variables to values. See comment of mhphf2 42608. (Contributed by SN, 23-Nov-2024.) |
| ⊢ 𝑄 = ((𝐼 evalSub 𝑆)‘𝑅) & ⊢ 𝐻 = (𝐼 mHomP 𝑈) & ⊢ 𝑈 = (𝑆 ↾s 𝑅) & ⊢ 𝐾 = (Base‘𝑆) & ⊢ 𝐹 = (𝑆 freeLMod 𝐼) & ⊢ 𝑀 = (Base‘𝐹) & ⊢ ∙ = ( ·𝑠 ‘𝐹) & ⊢ · = (.r‘𝑆) & ⊢ ↑ = (.g‘(mulGrp‘𝑆)) & ⊢ (𝜑 → 𝑆 ∈ CRing) & ⊢ (𝜑 → 𝑅 ∈ (SubRing‘𝑆)) & ⊢ (𝜑 → 𝐿 ∈ 𝑅) & ⊢ (𝜑 → 𝑋 ∈ (𝐻‘𝑁)) & ⊢ (𝜑 → 𝐴 ∈ 𝑀) ⇒ ⊢ (𝜑 → ((𝑄‘𝑋)‘(𝐿 ∙ 𝐴)) = ((𝑁 ↑ 𝐿) · ((𝑄‘𝑋)‘𝐴))) | ||
| Theorem | mhphf4 42610 | A homogeneous polynomial defines a homogeneous function; this is mhphf3 42609 with evalSub collapsed to eval. (Contributed by SN, 23-Nov-2024.) |
| ⊢ 𝑄 = (𝐼 eval 𝑆) & ⊢ 𝐻 = (𝐼 mHomP 𝑆) & ⊢ 𝐾 = (Base‘𝑆) & ⊢ 𝐹 = (𝑆 freeLMod 𝐼) & ⊢ 𝑀 = (Base‘𝐹) & ⊢ ∙ = ( ·𝑠 ‘𝐹) & ⊢ · = (.r‘𝑆) & ⊢ ↑ = (.g‘(mulGrp‘𝑆)) & ⊢ (𝜑 → 𝑆 ∈ CRing) & ⊢ (𝜑 → 𝐿 ∈ 𝐾) & ⊢ (𝜑 → 𝑋 ∈ (𝐻‘𝑁)) & ⊢ (𝜑 → 𝐴 ∈ 𝑀) ⇒ ⊢ (𝜑 → ((𝑄‘𝑋)‘(𝐿 ∙ 𝐴)) = ((𝑁 ↑ 𝐿) · ((𝑄‘𝑋)‘𝐴))) | ||
Looking at a corner in 3D space, one can see three right angles. It is impossible to draw three lines in 2D space such that any two of these lines are perpendicular, but a good enough representation is made by casting lines from the 2D surface. Points along the same cast line are collapsed into one point on the 2D surface. In many cases, the 2D surface is smaller than whatever needs to be represented. If the lines cast were perpendicular to the 2D surface, then only areas as small as the 2D surface could be represented. To fix this, the lines need to get further apart as they go farther from the 2D surface. On the other side of the 2D surface the lines will get closer together and intersect at a point (because it's defined that way). From this perspective, two parallel lines in 3D space will be represented by two lines that seem to intersect at a point "at infinity". Considering all maximal classes of parallel lines on a 2D plane in 3D space, these classes will all appear to intersect at different points at infinity, forming a line at infinity. Therefore the real projective plane can be thought of as the real affine plane together with the line at infinity. The projective plane takes care of some exceptions that may be found in the affine plane. For example, consider the curve that is the zeroes of 𝑦 = 𝑥↑2. Any line connecting the point (0, 1) to the x-axis intersects with the curve twice, except for the vertical line between (0, 1) and (0, 0). In the projective plane, the curve becomes an ellipse and there is no exception. While it may not seem like it, points at infinity and points corresponding to the affine plane are the same type of point. Consider a line going through the origin in 3D (affine) space. Either it intersects the plane 𝑧 = 1 once, or it is entirely within the plane 𝑧 = 0. If it is entirely within the plane 𝑧 = 0, then it corresponds to the point at infinity intersecting all lines on the plane 𝑧 = 1 with the same slope. Else it corresponds to the point in the 2D plane 𝑧 = 1 that it intersects. So there is a bijection between 3D lines through the origin and points on the real projective plane. The concept of projective spaces generalizes the projective plane to any dimension. | ||
| Syntax | cprjsp 42611 | Extend class notation with the projective space function. |
| class ℙ𝕣𝕠𝕛 | ||
| Definition | df-prjsp 42612* | Define the projective space function. In the bijection between 3D lines through the origin and points in the projective plane (see section comment), this is equivalent to making any two 3D points (excluding the origin) equivalent iff one is a multiple of another. This definition does not quite give all the properties needed, since the scalars of a left vector space can be "less dense" than the vectors (for example, making equivalent rational multiples of real numbers). Compare df-lsatoms 38977. (Contributed by BJ and SN, 29-Apr-2023.) |
| ⊢ ℙ𝕣𝕠𝕛 = (𝑣 ∈ LVec ↦ ⦋((Base‘𝑣) ∖ {(0g‘𝑣)}) / 𝑏⦌(𝑏 / {〈𝑥, 𝑦〉 ∣ ((𝑥 ∈ 𝑏 ∧ 𝑦 ∈ 𝑏) ∧ ∃𝑙 ∈ (Base‘(Scalar‘𝑣))𝑥 = (𝑙( ·𝑠 ‘𝑣)𝑦))})) | ||
| Theorem | prjspval 42613* | Value of the projective space function, which is also known as the projectivization of 𝑉. (Contributed by Steven Nguyen, 29-Apr-2023.) |
| ⊢ 𝐵 = ((Base‘𝑉) ∖ {(0g‘𝑉)}) & ⊢ · = ( ·𝑠 ‘𝑉) & ⊢ 𝑆 = (Scalar‘𝑉) & ⊢ 𝐾 = (Base‘𝑆) ⇒ ⊢ (𝑉 ∈ LVec → (ℙ𝕣𝕠𝕛‘𝑉) = (𝐵 / {〈𝑥, 𝑦〉 ∣ ((𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵) ∧ ∃𝑙 ∈ 𝐾 𝑥 = (𝑙 · 𝑦))})) | ||
| Theorem | prjsprel 42614* | Utility theorem regarding the relation used in ℙ𝕣𝕠𝕛. (Contributed by Steven Nguyen, 29-Apr-2023.) |
| ⊢ ∼ = {〈𝑥, 𝑦〉 ∣ ((𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵) ∧ ∃𝑙 ∈ 𝐾 𝑥 = (𝑙 · 𝑦))} ⇒ ⊢ (𝑋 ∼ 𝑌 ↔ ((𝑋 ∈ 𝐵 ∧ 𝑌 ∈ 𝐵) ∧ ∃𝑚 ∈ 𝐾 𝑋 = (𝑚 · 𝑌))) | ||
| Theorem | prjspertr 42615* | The relation in ℙ𝕣𝕠𝕛 is transitive. (Contributed by Steven Nguyen, 1-May-2023.) |
| ⊢ ∼ = {〈𝑥, 𝑦〉 ∣ ((𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵) ∧ ∃𝑙 ∈ 𝐾 𝑥 = (𝑙 · 𝑦))} & ⊢ 𝐵 = ((Base‘𝑉) ∖ {(0g‘𝑉)}) & ⊢ 𝑆 = (Scalar‘𝑉) & ⊢ · = ( ·𝑠 ‘𝑉) & ⊢ 𝐾 = (Base‘𝑆) ⇒ ⊢ ((𝑉 ∈ LMod ∧ (𝑋 ∼ 𝑌 ∧ 𝑌 ∼ 𝑍)) → 𝑋 ∼ 𝑍) | ||
| Theorem | prjsperref 42616* | The relation in ℙ𝕣𝕠𝕛 is reflexive. (Contributed by Steven Nguyen, 30-Apr-2023.) |
| ⊢ ∼ = {〈𝑥, 𝑦〉 ∣ ((𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵) ∧ ∃𝑙 ∈ 𝐾 𝑥 = (𝑙 · 𝑦))} & ⊢ 𝐵 = ((Base‘𝑉) ∖ {(0g‘𝑉)}) & ⊢ 𝑆 = (Scalar‘𝑉) & ⊢ · = ( ·𝑠 ‘𝑉) & ⊢ 𝐾 = (Base‘𝑆) ⇒ ⊢ (𝑉 ∈ LMod → (𝑋 ∈ 𝐵 ↔ 𝑋 ∼ 𝑋)) | ||
| Theorem | prjspersym 42617* | The relation in ℙ𝕣𝕠𝕛 is symmetric. (Contributed by Steven Nguyen, 1-May-2023.) |
| ⊢ ∼ = {〈𝑥, 𝑦〉 ∣ ((𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵) ∧ ∃𝑙 ∈ 𝐾 𝑥 = (𝑙 · 𝑦))} & ⊢ 𝐵 = ((Base‘𝑉) ∖ {(0g‘𝑉)}) & ⊢ 𝑆 = (Scalar‘𝑉) & ⊢ · = ( ·𝑠 ‘𝑉) & ⊢ 𝐾 = (Base‘𝑆) ⇒ ⊢ ((𝑉 ∈ LVec ∧ 𝑋 ∼ 𝑌) → 𝑌 ∼ 𝑋) | ||
| Theorem | prjsper 42618* | The relation used to define ℙ𝕣𝕠𝕛 is an equivalence relation. (Contributed by Steven Nguyen, 1-May-2023.) |
| ⊢ ∼ = {〈𝑥, 𝑦〉 ∣ ((𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵) ∧ ∃𝑙 ∈ 𝐾 𝑥 = (𝑙 · 𝑦))} & ⊢ 𝐵 = ((Base‘𝑉) ∖ {(0g‘𝑉)}) & ⊢ 𝑆 = (Scalar‘𝑉) & ⊢ · = ( ·𝑠 ‘𝑉) & ⊢ 𝐾 = (Base‘𝑆) ⇒ ⊢ (𝑉 ∈ LVec → ∼ Er 𝐵) | ||
| Theorem | prjspreln0 42619* | Two nonzero vectors are equivalent by a nonzero scalar. (Contributed by Steven Nguyen, 31-May-2023.) |
| ⊢ ∼ = {〈𝑥, 𝑦〉 ∣ ((𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵) ∧ ∃𝑙 ∈ 𝐾 𝑥 = (𝑙 · 𝑦))} & ⊢ 𝐵 = ((Base‘𝑉) ∖ {(0g‘𝑉)}) & ⊢ 𝑆 = (Scalar‘𝑉) & ⊢ · = ( ·𝑠 ‘𝑉) & ⊢ 𝐾 = (Base‘𝑆) & ⊢ 0 = (0g‘𝑆) ⇒ ⊢ (𝑉 ∈ LVec → (𝑋 ∼ 𝑌 ↔ ((𝑋 ∈ 𝐵 ∧ 𝑌 ∈ 𝐵) ∧ ∃𝑚 ∈ (𝐾 ∖ { 0 })𝑋 = (𝑚 · 𝑌)))) | ||
| Theorem | prjspvs 42620* | A nonzero multiple of a vector is equivalent to the vector. (Contributed by Steven Nguyen, 6-Jun-2023.) |
| ⊢ ∼ = {〈𝑥, 𝑦〉 ∣ ((𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵) ∧ ∃𝑙 ∈ 𝐾 𝑥 = (𝑙 · 𝑦))} & ⊢ 𝐵 = ((Base‘𝑉) ∖ {(0g‘𝑉)}) & ⊢ 𝑆 = (Scalar‘𝑉) & ⊢ · = ( ·𝑠 ‘𝑉) & ⊢ 𝐾 = (Base‘𝑆) & ⊢ 0 = (0g‘𝑆) ⇒ ⊢ ((𝑉 ∈ LVec ∧ 𝑋 ∈ 𝐵 ∧ 𝑁 ∈ (𝐾 ∖ { 0 })) → (𝑁 · 𝑋) ∼ 𝑋) | ||
| Theorem | prjsprellsp 42621* | Two vectors are equivalent iff their spans are equal. (Contributed by Steven Nguyen, 31-May-2023.) |
| ⊢ ∼ = {〈𝑥, 𝑦〉 ∣ ((𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵) ∧ ∃𝑙 ∈ 𝐾 𝑥 = (𝑙 · 𝑦))} & ⊢ 𝐵 = ((Base‘𝑉) ∖ {(0g‘𝑉)}) & ⊢ 𝑆 = (Scalar‘𝑉) & ⊢ · = ( ·𝑠 ‘𝑉) & ⊢ 𝐾 = (Base‘𝑆) & ⊢ 𝑁 = (LSpan‘𝑉) ⇒ ⊢ ((𝑉 ∈ LVec ∧ (𝑋 ∈ 𝐵 ∧ 𝑌 ∈ 𝐵)) → (𝑋 ∼ 𝑌 ↔ (𝑁‘{𝑋}) = (𝑁‘{𝑌}))) | ||
| Theorem | prjspeclsp 42622* | The vectors equivalent to a vector 𝑋 are the nonzero vectors in the span of 𝑋. (Contributed by Steven Nguyen, 6-Jun-2023.) |
| ⊢ ∼ = {〈𝑥, 𝑦〉 ∣ ((𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵) ∧ ∃𝑙 ∈ 𝐾 𝑥 = (𝑙 · 𝑦))} & ⊢ 𝐵 = ((Base‘𝑉) ∖ {(0g‘𝑉)}) & ⊢ 𝑆 = (Scalar‘𝑉) & ⊢ · = ( ·𝑠 ‘𝑉) & ⊢ 𝐾 = (Base‘𝑆) & ⊢ 𝑁 = (LSpan‘𝑉) ⇒ ⊢ ((𝑉 ∈ LVec ∧ 𝑋 ∈ 𝐵) → [𝑋] ∼ = ((𝑁‘{𝑋}) ∖ {(0g‘𝑉)})) | ||
| Theorem | prjspval2 42623* | Alternate definition of projective space. (Contributed by Steven Nguyen, 7-Jun-2023.) |
| ⊢ 0 = (0g‘𝑉) & ⊢ 𝐵 = ((Base‘𝑉) ∖ { 0 }) & ⊢ 𝑁 = (LSpan‘𝑉) ⇒ ⊢ (𝑉 ∈ LVec → (ℙ𝕣𝕠𝕛‘𝑉) = ∪ 𝑧 ∈ 𝐵 {((𝑁‘{𝑧}) ∖ { 0 })}) | ||
| Syntax | cprjspn 42624 | Extend class notation with the n-dimensional projective space function. |
| class ℙ𝕣𝕠𝕛n | ||
| Definition | df-prjspn 42625* | Define the n-dimensional projective space function. A projective space of dimension 1 is a projective line, and a projective space of dimension 2 is a projective plane. Compare df-ehl 25420. This space is considered n-dimensional because the vector space (𝑘 freeLMod (0...𝑛)) is (n+1)-dimensional and the ℙ𝕣𝕠𝕛 function returns equivalence classes with respect to a linear (1-dimensional) relation. (Contributed by BJ and Steven Nguyen, 29-Apr-2023.) |
| ⊢ ℙ𝕣𝕠𝕛n = (𝑛 ∈ ℕ0, 𝑘 ∈ DivRing ↦ (ℙ𝕣𝕠𝕛‘(𝑘 freeLMod (0...𝑛)))) | ||
| Theorem | prjspnval 42626 | Value of the n-dimensional projective space function. (Contributed by Steven Nguyen, 1-May-2023.) |
| ⊢ ((𝑁 ∈ ℕ0 ∧ 𝐾 ∈ DivRing) → (𝑁ℙ𝕣𝕠𝕛n𝐾) = (ℙ𝕣𝕠𝕛‘(𝐾 freeLMod (0...𝑁)))) | ||
| Theorem | prjspnerlem 42627* | A lemma showing that the equivalence relation used in prjspnval2 42628 and the equivalence relation used in prjspval 42613 are equal, but only with the antecedent 𝐾 ∈ DivRing. (Contributed by SN, 15-Jul-2023.) |
| ⊢ ∼ = {〈𝑥, 𝑦〉 ∣ ((𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵) ∧ ∃𝑙 ∈ 𝑆 𝑥 = (𝑙 · 𝑦))} & ⊢ 𝑊 = (𝐾 freeLMod (0...𝑁)) & ⊢ 𝐵 = ((Base‘𝑊) ∖ {(0g‘𝑊)}) & ⊢ 𝑆 = (Base‘𝐾) & ⊢ · = ( ·𝑠 ‘𝑊) ⇒ ⊢ (𝐾 ∈ DivRing → ∼ = {〈𝑥, 𝑦〉 ∣ ((𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵) ∧ ∃𝑙 ∈ (Base‘(Scalar‘𝑊))𝑥 = (𝑙 · 𝑦))}) | ||
| Theorem | prjspnval2 42628* | Value of the n-dimensional projective space function, expanded. (Contributed by Steven Nguyen, 15-Jul-2023.) |
| ⊢ ∼ = {〈𝑥, 𝑦〉 ∣ ((𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵) ∧ ∃𝑙 ∈ 𝑆 𝑥 = (𝑙 · 𝑦))} & ⊢ 𝑊 = (𝐾 freeLMod (0...𝑁)) & ⊢ 𝐵 = ((Base‘𝑊) ∖ {(0g‘𝑊)}) & ⊢ 𝑆 = (Base‘𝐾) & ⊢ · = ( ·𝑠 ‘𝑊) ⇒ ⊢ ((𝑁 ∈ ℕ0 ∧ 𝐾 ∈ DivRing) → (𝑁ℙ𝕣𝕠𝕛n𝐾) = (𝐵 / ∼ )) | ||
| Theorem | prjspner 42629* | The relation used to define ℙ𝕣𝕠𝕛 (and indirectly ℙ𝕣𝕠𝕛n through df-prjspn 42625) is an equivalence relation. This is a lemma that converts the equivalence relation used in results like prjspertr 42615 and prjspersym 42617 (see prjspnerlem 42627). Several theorems are covered in one thanks to the theorems around df-er 8745. (Contributed by SN, 14-Aug-2023.) |
| ⊢ ∼ = {〈𝑥, 𝑦〉 ∣ ((𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵) ∧ ∃𝑙 ∈ 𝑆 𝑥 = (𝑙 · 𝑦))} & ⊢ 𝑊 = (𝐾 freeLMod (0...𝑁)) & ⊢ 𝐵 = ((Base‘𝑊) ∖ {(0g‘𝑊)}) & ⊢ 𝑆 = (Base‘𝐾) & ⊢ · = ( ·𝑠 ‘𝑊) & ⊢ (𝜑 → 𝐾 ∈ DivRing) ⇒ ⊢ (𝜑 → ∼ Er 𝐵) | ||
| Theorem | prjspnvs 42630* | A nonzero multiple of a vector is equivalent to the vector. This converts the equivalence relation used in prjspvs 42620 (see prjspnerlem 42627). (Contributed by SN, 8-Aug-2024.) |
| ⊢ ∼ = {〈𝑥, 𝑦〉 ∣ ((𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵) ∧ ∃𝑙 ∈ 𝑆 𝑥 = (𝑙 · 𝑦))} & ⊢ 𝑊 = (𝐾 freeLMod (0...𝑁)) & ⊢ 𝐵 = ((Base‘𝑊) ∖ {(0g‘𝑊)}) & ⊢ 𝑆 = (Base‘𝐾) & ⊢ · = ( ·𝑠 ‘𝑊) & ⊢ 0 = (0g‘𝐾) & ⊢ (𝜑 → 𝐾 ∈ DivRing) & ⊢ (𝜑 → 𝑋 ∈ 𝐵) & ⊢ (𝜑 → 𝐶 ∈ 𝑆) & ⊢ (𝜑 → 𝐶 ≠ 0 ) ⇒ ⊢ (𝜑 → (𝐶 · 𝑋) ∼ 𝑋) | ||
| Theorem | prjspnssbas 42631 | A projective point spans a subset of the (nonzero) affine points. (Contributed by SN, 17-Jan-2025.) |
| ⊢ 𝑃 = (𝑁ℙ𝕣𝕠𝕛n𝐾) & ⊢ 𝑊 = (𝐾 freeLMod (0...𝑁)) & ⊢ 𝐵 = ((Base‘𝑊) ∖ {(0g‘𝑊)}) & ⊢ (𝜑 → 𝑁 ∈ ℕ0) & ⊢ (𝜑 → 𝐾 ∈ DivRing) ⇒ ⊢ (𝜑 → 𝑃 ⊆ 𝒫 𝐵) | ||
| Theorem | prjspnn0 42632 | A projective point is nonempty. (Contributed by SN, 17-Jan-2025.) |
| ⊢ 𝑃 = (𝑁ℙ𝕣𝕠𝕛n𝐾) & ⊢ 𝑊 = (𝐾 freeLMod (0...𝑁)) & ⊢ 𝐵 = ((Base‘𝑊) ∖ {(0g‘𝑊)}) & ⊢ (𝜑 → 𝑁 ∈ ℕ0) & ⊢ (𝜑 → 𝐾 ∈ DivRing) & ⊢ (𝜑 → 𝐴 ∈ 𝑃) ⇒ ⊢ (𝜑 → 𝐴 ≠ ∅) | ||
| Theorem | 0prjspnlem 42633 | Lemma for 0prjspn 42638. The given unit vector is a nonzero vector. (Contributed by Steven Nguyen, 16-Jul-2023.) |
| ⊢ 𝐵 = ((Base‘𝑊) ∖ {(0g‘𝑊)}) & ⊢ 𝑊 = (𝐾 freeLMod (0...0)) & ⊢ 1 = ((𝐾 unitVec (0...0))‘0) ⇒ ⊢ (𝐾 ∈ DivRing → 1 ∈ 𝐵) | ||
| Theorem | prjspnfv01 42634* | Any vector is equivalent to a vector whose zeroth coordinate is 0 or 1 (proof of the value of the zeroth coordinate). (Contributed by SN, 13-Aug-2023.) |
| ⊢ 𝐹 = (𝑏 ∈ 𝐵 ↦ if((𝑏‘0) = 0 , 𝑏, ((𝐼‘(𝑏‘0)) · 𝑏))) & ⊢ 𝐵 = ((Base‘𝑊) ∖ {(0g‘𝑊)}) & ⊢ 𝑊 = (𝐾 freeLMod (0...𝑁)) & ⊢ · = ( ·𝑠 ‘𝑊) & ⊢ 0 = (0g‘𝐾) & ⊢ 1 = (1r‘𝐾) & ⊢ 𝐼 = (invr‘𝐾) & ⊢ (𝜑 → 𝐾 ∈ DivRing) & ⊢ (𝜑 → 𝑁 ∈ ℕ0) & ⊢ (𝜑 → 𝑋 ∈ 𝐵) ⇒ ⊢ (𝜑 → ((𝐹‘𝑋)‘0) = if((𝑋‘0) = 0 , 0 , 1 )) | ||
| Theorem | prjspner01 42635* | Any vector is equivalent to a vector whose zeroth coordinate is 0 or 1 (proof of the equivalence). (Contributed by SN, 13-Aug-2023.) |
| ⊢ ∼ = {〈𝑥, 𝑦〉 ∣ ((𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵) ∧ ∃𝑙 ∈ 𝑆 𝑥 = (𝑙 · 𝑦))} & ⊢ 𝐹 = (𝑏 ∈ 𝐵 ↦ if((𝑏‘0) = 0 , 𝑏, ((𝐼‘(𝑏‘0)) · 𝑏))) & ⊢ 𝐵 = ((Base‘𝑊) ∖ {(0g‘𝑊)}) & ⊢ 𝑊 = (𝐾 freeLMod (0...𝑁)) & ⊢ · = ( ·𝑠 ‘𝑊) & ⊢ 𝑆 = (Base‘𝐾) & ⊢ 0 = (0g‘𝐾) & ⊢ 𝐼 = (invr‘𝐾) & ⊢ (𝜑 → 𝐾 ∈ DivRing) & ⊢ (𝜑 → 𝑁 ∈ ℕ0) & ⊢ (𝜑 → 𝑋 ∈ 𝐵) ⇒ ⊢ (𝜑 → 𝑋 ∼ (𝐹‘𝑋)) | ||
| Theorem | prjspner1 42636* | Two vectors whose zeroth coordinate is nonzero are equivalent if and only if they have the same representative in the (n-1)-dimensional affine subspace { x0 = 1 } . For example, vectors in 3D space whose 𝑥 coordinate is nonzero are equivalent iff they intersect at the plane 𝑥 = 1 at the same point (also see section header). (Contributed by SN, 13-Aug-2023.) |
| ⊢ ∼ = {〈𝑥, 𝑦〉 ∣ ((𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵) ∧ ∃𝑙 ∈ 𝑆 𝑥 = (𝑙 · 𝑦))} & ⊢ 𝐹 = (𝑏 ∈ 𝐵 ↦ if((𝑏‘0) = 0 , 𝑏, ((𝐼‘(𝑏‘0)) · 𝑏))) & ⊢ 𝐵 = ((Base‘𝑊) ∖ {(0g‘𝑊)}) & ⊢ 𝑊 = (𝐾 freeLMod (0...𝑁)) & ⊢ · = ( ·𝑠 ‘𝑊) & ⊢ 𝑆 = (Base‘𝐾) & ⊢ 0 = (0g‘𝐾) & ⊢ 𝐼 = (invr‘𝐾) & ⊢ (𝜑 → 𝐾 ∈ DivRing) & ⊢ (𝜑 → 𝑁 ∈ ℕ0) & ⊢ (𝜑 → 𝑋 ∈ 𝐵) & ⊢ (𝜑 → 𝑌 ∈ 𝐵) & ⊢ (𝜑 → (𝑋‘0) ≠ 0 ) & ⊢ (𝜑 → (𝑌‘0) ≠ 0 ) ⇒ ⊢ (𝜑 → (𝑋 ∼ 𝑌 ↔ (𝐹‘𝑋) = (𝐹‘𝑌))) | ||
| Theorem | 0prjspnrel 42637* | In the zero-dimensional projective space, all vectors are equivalent to the unit vector. (Contributed by Steven Nguyen, 7-Jun-2023.) |
| ⊢ ∼ = {〈𝑥, 𝑦〉 ∣ ((𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵) ∧ ∃𝑙 ∈ 𝑆 𝑥 = (𝑙 · 𝑦))} & ⊢ 𝐵 = ((Base‘𝑊) ∖ {(0g‘𝑊)}) & ⊢ · = ( ·𝑠 ‘𝑊) & ⊢ 𝑆 = (Base‘𝐾) & ⊢ 𝑊 = (𝐾 freeLMod (0...0)) & ⊢ 1 = ((𝐾 unitVec (0...0))‘0) ⇒ ⊢ ((𝐾 ∈ DivRing ∧ 𝑋 ∈ 𝐵) → 𝑋 ∼ 1 ) | ||
| Theorem | 0prjspn 42638 | A zero-dimensional projective space has only 1 point. (Contributed by Steven Nguyen, 9-Jun-2023.) |
| ⊢ 𝑊 = (𝐾 freeLMod (0...0)) & ⊢ 𝐵 = ((Base‘𝑊) ∖ {(0g‘𝑊)}) ⇒ ⊢ (𝐾 ∈ DivRing → (0ℙ𝕣𝕠𝕛n𝐾) = {𝐵}) | ||
| Syntax | cprjcrv 42639 | Extend class notation with the projective curve function. |
| class ℙ𝕣𝕠𝕛Crv | ||
| Definition | df-prjcrv 42640* | Define the projective curve function. This takes a homogeneous polynomial and outputs the homogeneous coordinates where the polynomial evaluates to zero (the "zero set"). (In other words, scalar multiples are collapsed into the same projective point. See mhphf4 42610 and prjspvs 42620). (Contributed by SN, 23-Nov-2024.) |
| ⊢ ℙ𝕣𝕠𝕛Crv = (𝑛 ∈ ℕ0, 𝑘 ∈ Field ↦ (𝑓 ∈ ∪ ran ((0...𝑛) mHomP 𝑘) ↦ {𝑝 ∈ (𝑛ℙ𝕣𝕠𝕛n𝑘) ∣ ((((0...𝑛) eval 𝑘)‘𝑓) “ 𝑝) = {(0g‘𝑘)}})) | ||
| Theorem | prjcrvfval 42641* | Value of the projective curve function. (Contributed by SN, 23-Nov-2024.) |
| ⊢ 𝐻 = ((0...𝑁) mHomP 𝐾) & ⊢ 𝐸 = ((0...𝑁) eval 𝐾) & ⊢ 𝑃 = (𝑁ℙ𝕣𝕠𝕛n𝐾) & ⊢ 0 = (0g‘𝐾) & ⊢ (𝜑 → 𝑁 ∈ ℕ0) & ⊢ (𝜑 → 𝐾 ∈ Field) ⇒ ⊢ (𝜑 → (𝑁ℙ𝕣𝕠𝕛Crv𝐾) = (𝑓 ∈ ∪ ran 𝐻 ↦ {𝑝 ∈ 𝑃 ∣ ((𝐸‘𝑓) “ 𝑝) = { 0 }})) | ||
| Theorem | prjcrvval 42642* | Value of the projective curve function. (Contributed by SN, 23-Nov-2024.) |
| ⊢ 𝐻 = ((0...𝑁) mHomP 𝐾) & ⊢ 𝐸 = ((0...𝑁) eval 𝐾) & ⊢ 𝑃 = (𝑁ℙ𝕣𝕠𝕛n𝐾) & ⊢ 0 = (0g‘𝐾) & ⊢ (𝜑 → 𝑁 ∈ ℕ0) & ⊢ (𝜑 → 𝐾 ∈ Field) & ⊢ (𝜑 → 𝐹 ∈ ∪ ran 𝐻) ⇒ ⊢ (𝜑 → ((𝑁ℙ𝕣𝕠𝕛Crv𝐾)‘𝐹) = {𝑝 ∈ 𝑃 ∣ ((𝐸‘𝐹) “ 𝑝) = { 0 }}) | ||
| Theorem | prjcrv0 42643 | The "curve" (zero set) corresponding to the zero polynomial contains all coordinates. (Contributed by SN, 23-Nov-2024.) |
| ⊢ 𝑌 = ((0...𝑁) mPoly 𝐾) & ⊢ 0 = (0g‘𝑌) & ⊢ 𝑃 = (𝑁ℙ𝕣𝕠𝕛n𝐾) & ⊢ (𝜑 → 𝑁 ∈ ℕ0) & ⊢ (𝜑 → 𝐾 ∈ Field) ⇒ ⊢ (𝜑 → ((𝑁ℙ𝕣𝕠𝕛Crv𝐾)‘ 0 ) = 𝑃) | ||
| Theorem | dffltz 42644* | Fermat's Last Theorem (FLT) for nonzero integers is equivalent to the original scope of natural numbers. The backwards direction takes (𝑎↑𝑛) + (𝑏↑𝑛) = (𝑐↑𝑛), and adds the negative of any negative term to both sides, thus creating the corresponding equation with only positive integers. There are six combinations of negativity, so the proof is particularly long. (Contributed by Steven Nguyen, 27-Feb-2023.) |
| ⊢ (∀𝑛 ∈ (ℤ≥‘3)∀𝑥 ∈ ℕ ∀𝑦 ∈ ℕ ∀𝑧 ∈ ℕ ((𝑥↑𝑛) + (𝑦↑𝑛)) ≠ (𝑧↑𝑛) ↔ ∀𝑛 ∈ (ℤ≥‘3)∀𝑎 ∈ (ℤ ∖ {0})∀𝑏 ∈ (ℤ ∖ {0})∀𝑐 ∈ (ℤ ∖ {0})((𝑎↑𝑛) + (𝑏↑𝑛)) ≠ (𝑐↑𝑛)) | ||
| Theorem | fltmul 42645 | A counterexample to FLT stays valid when scaled. The hypotheses are more general than they need to be for convenience. (There does not seem to be a standard term for Fermat or Pythagorean triples extended to any 𝑁 ∈ ℕ0, so the label is more about the context in which this theorem is used). (Contributed by SN, 20-Aug-2024.) |
| ⊢ (𝜑 → 𝑆 ∈ ℂ) & ⊢ (𝜑 → 𝐴 ∈ ℂ) & ⊢ (𝜑 → 𝐵 ∈ ℂ) & ⊢ (𝜑 → 𝐶 ∈ ℂ) & ⊢ (𝜑 → 𝑁 ∈ ℕ0) & ⊢ (𝜑 → ((𝐴↑𝑁) + (𝐵↑𝑁)) = (𝐶↑𝑁)) ⇒ ⊢ (𝜑 → (((𝑆 · 𝐴)↑𝑁) + ((𝑆 · 𝐵)↑𝑁)) = ((𝑆 · 𝐶)↑𝑁)) | ||
| Theorem | fltdiv 42646 | A counterexample to FLT stays valid when scaled. The hypotheses are more general than they need to be for convenience. (Contributed by SN, 20-Aug-2024.) |
| ⊢ (𝜑 → 𝑆 ∈ ℂ) & ⊢ (𝜑 → 𝑆 ≠ 0) & ⊢ (𝜑 → 𝐴 ∈ ℂ) & ⊢ (𝜑 → 𝐵 ∈ ℂ) & ⊢ (𝜑 → 𝐶 ∈ ℂ) & ⊢ (𝜑 → 𝑁 ∈ ℕ0) & ⊢ (𝜑 → ((𝐴↑𝑁) + (𝐵↑𝑁)) = (𝐶↑𝑁)) ⇒ ⊢ (𝜑 → (((𝐴 / 𝑆)↑𝑁) + ((𝐵 / 𝑆)↑𝑁)) = ((𝐶 / 𝑆)↑𝑁)) | ||
| Theorem | flt0 42647 | A counterexample for FLT does not exist for 𝑁 = 0. (Contributed by SN, 20-Aug-2024.) |
| ⊢ (𝜑 → 𝐴 ∈ ℂ) & ⊢ (𝜑 → 𝐵 ∈ ℂ) & ⊢ (𝜑 → 𝐶 ∈ ℂ) & ⊢ (𝜑 → 𝑁 ∈ ℕ0) & ⊢ (𝜑 → ((𝐴↑𝑁) + (𝐵↑𝑁)) = (𝐶↑𝑁)) ⇒ ⊢ (𝜑 → 𝑁 ∈ ℕ) | ||
| Theorem | fltdvdsabdvdsc 42648 | Any factor of both 𝐴 and 𝐵 also divides 𝐶. This establishes the validity of fltabcoprmex 42649. (Contributed by SN, 21-Aug-2024.) |
| ⊢ (𝜑 → 𝐴 ∈ ℕ) & ⊢ (𝜑 → 𝐵 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ ℕ) & ⊢ (𝜑 → 𝑁 ∈ ℕ) & ⊢ (𝜑 → ((𝐴↑𝑁) + (𝐵↑𝑁)) = (𝐶↑𝑁)) ⇒ ⊢ (𝜑 → (𝐴 gcd 𝐵) ∥ 𝐶) | ||
| Theorem | fltabcoprmex 42649 | A counterexample to FLT implies a counterexample to FLT with 𝐴, 𝐵 (assigned to 𝐴 / (𝐴 gcd 𝐵) and 𝐵 / (𝐴 gcd 𝐵)) coprime (by divgcdcoprm0 16702). (Contributed by SN, 20-Aug-2024.) |
| ⊢ (𝜑 → 𝐴 ∈ ℕ) & ⊢ (𝜑 → 𝐵 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ ℕ) & ⊢ (𝜑 → 𝑁 ∈ ℕ0) & ⊢ (𝜑 → ((𝐴↑𝑁) + (𝐵↑𝑁)) = (𝐶↑𝑁)) ⇒ ⊢ (𝜑 → (((𝐴 / (𝐴 gcd 𝐵))↑𝑁) + ((𝐵 / (𝐴 gcd 𝐵))↑𝑁)) = ((𝐶 / (𝐴 gcd 𝐵))↑𝑁)) | ||
| Theorem | fltaccoprm 42650 | A counterexample to FLT with 𝐴, 𝐵 coprime also has 𝐴, 𝐶 coprime. (Contributed by SN, 20-Aug-2024.) |
| ⊢ (𝜑 → 𝐴 ∈ ℕ) & ⊢ (𝜑 → 𝐵 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ ℕ) & ⊢ (𝜑 → 𝑁 ∈ ℕ0) & ⊢ (𝜑 → ((𝐴↑𝑁) + (𝐵↑𝑁)) = (𝐶↑𝑁)) & ⊢ (𝜑 → (𝐴 gcd 𝐵) = 1) ⇒ ⊢ (𝜑 → (𝐴 gcd 𝐶) = 1) | ||
| Theorem | fltbccoprm 42651 | A counterexample to FLT with 𝐴, 𝐵 coprime also has 𝐵, 𝐶 coprime. Proven from fltaccoprm 42650 using commutativity of addition. (Contributed by SN, 20-Aug-2024.) |
| ⊢ (𝜑 → 𝐴 ∈ ℕ) & ⊢ (𝜑 → 𝐵 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ ℕ) & ⊢ (𝜑 → 𝑁 ∈ ℕ0) & ⊢ (𝜑 → ((𝐴↑𝑁) + (𝐵↑𝑁)) = (𝐶↑𝑁)) & ⊢ (𝜑 → (𝐴 gcd 𝐵) = 1) ⇒ ⊢ (𝜑 → (𝐵 gcd 𝐶) = 1) | ||
| Theorem | fltabcoprm 42652 | A counterexample to FLT with 𝐴, 𝐶 coprime also has 𝐴, 𝐵 coprime. Converse of fltaccoprm 42650. (Contributed by SN, 22-Aug-2024.) |
| ⊢ (𝜑 → 𝐴 ∈ ℕ) & ⊢ (𝜑 → 𝐵 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ ℕ) & ⊢ (𝜑 → (𝐴 gcd 𝐶) = 1) & ⊢ (𝜑 → ((𝐴↑2) + (𝐵↑2)) = (𝐶↑2)) ⇒ ⊢ (𝜑 → (𝐴 gcd 𝐵) = 1) | ||
| Theorem | infdesc 42653* | Infinite descent. The hypotheses say that 𝑆 is lower bounded, and that if 𝜓 holds for an integer in 𝑆, it holds for a smaller integer in 𝑆. By infinite descent, eventually we cannot go any smaller, therefore 𝜓 holds for no integer in 𝑆. (Contributed by SN, 20-Aug-2024.) |
| ⊢ (𝑦 = 𝑥 → (𝜓 ↔ 𝜒)) & ⊢ (𝑦 = 𝑧 → (𝜓 ↔ 𝜃)) & ⊢ (𝜑 → 𝑆 ⊆ (ℤ≥‘𝑀)) & ⊢ ((𝜑 ∧ (𝑥 ∈ 𝑆 ∧ 𝜒)) → ∃𝑧 ∈ 𝑆 (𝜃 ∧ 𝑧 < 𝑥)) ⇒ ⊢ (𝜑 → {𝑦 ∈ 𝑆 ∣ 𝜓} = ∅) | ||
| Theorem | fltne 42654 | If a counterexample to FLT exists, its addends are not equal. (Contributed by SN, 1-Jun-2023.) |
| ⊢ (𝜑 → 𝐴 ∈ ℕ) & ⊢ (𝜑 → 𝐵 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ ℕ) & ⊢ (𝜑 → 𝑁 ∈ (ℤ≥‘2)) & ⊢ (𝜑 → ((𝐴↑𝑁) + (𝐵↑𝑁)) = (𝐶↑𝑁)) ⇒ ⊢ (𝜑 → 𝐴 ≠ 𝐵) | ||
| Theorem | flt4lem 42655 | Raising a number to the fourth power is equivalent to squaring it twice. (Contributed by SN, 21-Aug-2024.) |
| ⊢ (𝜑 → 𝐴 ∈ ℂ) ⇒ ⊢ (𝜑 → (𝐴↑4) = ((𝐴↑2)↑2)) | ||
| Theorem | flt4lem1 42656 | Satisfy the antecedent used in several pythagtrip 16872 lemmas, with 𝐴, 𝐶 coprime rather than 𝐴, 𝐵. (Contributed by SN, 21-Aug-2024.) |
| ⊢ (𝜑 → 𝐴 ∈ ℕ) & ⊢ (𝜑 → 𝐵 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ ℕ) & ⊢ (𝜑 → ¬ 2 ∥ 𝐴) & ⊢ (𝜑 → (𝐴 gcd 𝐶) = 1) & ⊢ (𝜑 → ((𝐴↑2) + (𝐵↑2)) = (𝐶↑2)) ⇒ ⊢ (𝜑 → ((𝐴 ∈ ℕ ∧ 𝐵 ∈ ℕ ∧ 𝐶 ∈ ℕ) ∧ ((𝐴↑2) + (𝐵↑2)) = (𝐶↑2) ∧ ((𝐴 gcd 𝐵) = 1 ∧ ¬ 2 ∥ 𝐴))) | ||
| Theorem | flt4lem2 42657 | If 𝐴 is even, 𝐵 is odd. (Contributed by SN, 22-Aug-2024.) |
| ⊢ (𝜑 → 𝐴 ∈ ℕ) & ⊢ (𝜑 → 𝐵 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ ℕ) & ⊢ (𝜑 → 2 ∥ 𝐴) & ⊢ (𝜑 → (𝐴 gcd 𝐶) = 1) & ⊢ (𝜑 → ((𝐴↑2) + (𝐵↑2)) = (𝐶↑2)) ⇒ ⊢ (𝜑 → ¬ 2 ∥ 𝐵) | ||
| Theorem | flt4lem3 42658 | Equivalent to pythagtriplem4 16857. Show that 𝐶 + 𝐴 and 𝐶 − 𝐴 are coprime. (Contributed by SN, 22-Aug-2024.) |
| ⊢ (𝜑 → 𝐴 ∈ ℕ) & ⊢ (𝜑 → 𝐵 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ ℕ) & ⊢ (𝜑 → 2 ∥ 𝐴) & ⊢ (𝜑 → (𝐴 gcd 𝐶) = 1) & ⊢ (𝜑 → ((𝐴↑2) + (𝐵↑2)) = (𝐶↑2)) ⇒ ⊢ (𝜑 → ((𝐶 + 𝐴) gcd (𝐶 − 𝐴)) = 1) | ||
| Theorem | flt4lem4 42659 | If the product of two coprime factors is a perfect square, the factors are perfect squares. (Contributed by SN, 22-Aug-2024.) |
| ⊢ (𝜑 → 𝐴 ∈ ℕ) & ⊢ (𝜑 → 𝐵 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ ℕ) & ⊢ (𝜑 → (𝐴 gcd 𝐵) = 1) & ⊢ (𝜑 → (𝐴 · 𝐵) = (𝐶↑2)) ⇒ ⊢ (𝜑 → (𝐴 = ((𝐴 gcd 𝐶)↑2) ∧ 𝐵 = ((𝐵 gcd 𝐶)↑2))) | ||
| Theorem | flt4lem5 42660 | In the context of the lemmas of pythagtrip 16872, 𝑀 and 𝑁 are coprime. (Contributed by SN, 23-Aug-2024.) |
| ⊢ 𝑀 = (((√‘(𝐶 + 𝐵)) + (√‘(𝐶 − 𝐵))) / 2) & ⊢ 𝑁 = (((√‘(𝐶 + 𝐵)) − (√‘(𝐶 − 𝐵))) / 2) ⇒ ⊢ (((𝐴 ∈ ℕ ∧ 𝐵 ∈ ℕ ∧ 𝐶 ∈ ℕ) ∧ ((𝐴↑2) + (𝐵↑2)) = (𝐶↑2) ∧ ((𝐴 gcd 𝐵) = 1 ∧ ¬ 2 ∥ 𝐴)) → (𝑀 gcd 𝑁) = 1) | ||
| Theorem | flt4lem5elem 42661 | Version of fltaccoprm 42650 and fltbccoprm 42651 where 𝑀 is not squared. This can be proved in general for any polynomial in three variables: using prmdvdsncoprmbd 16764, dvds2addd 16329, and prmdvdsexp 16752, we can show that if two variables are coprime, the third is also coprime to the two. (Contributed by SN, 24-Aug-2024.) |
| ⊢ (𝜑 → 𝑀 ∈ ℕ) & ⊢ (𝜑 → 𝑅 ∈ ℕ) & ⊢ (𝜑 → 𝑆 ∈ ℕ) & ⊢ (𝜑 → 𝑀 = ((𝑅↑2) + (𝑆↑2))) & ⊢ (𝜑 → (𝑅 gcd 𝑆) = 1) ⇒ ⊢ (𝜑 → ((𝑅 gcd 𝑀) = 1 ∧ (𝑆 gcd 𝑀) = 1)) | ||
| Theorem | flt4lem5a 42662 | Part 1 of Equation 1 of https://crypto.stanford.edu/pbc/notes/numberfield/fermatn4.html. (Contributed by SN, 22-Aug-2024.) |
| ⊢ 𝑀 = (((√‘(𝐶 + (𝐵↑2))) + (√‘(𝐶 − (𝐵↑2)))) / 2) & ⊢ 𝑁 = (((√‘(𝐶 + (𝐵↑2))) − (√‘(𝐶 − (𝐵↑2)))) / 2) & ⊢ 𝑅 = (((√‘(𝑀 + 𝑁)) + (√‘(𝑀 − 𝑁))) / 2) & ⊢ 𝑆 = (((√‘(𝑀 + 𝑁)) − (√‘(𝑀 − 𝑁))) / 2) & ⊢ (𝜑 → 𝐴 ∈ ℕ) & ⊢ (𝜑 → 𝐵 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ ℕ) & ⊢ (𝜑 → ¬ 2 ∥ 𝐴) & ⊢ (𝜑 → (𝐴 gcd 𝐶) = 1) & ⊢ (𝜑 → ((𝐴↑4) + (𝐵↑4)) = (𝐶↑2)) ⇒ ⊢ (𝜑 → ((𝐴↑2) + (𝑁↑2)) = (𝑀↑2)) | ||
| Theorem | flt4lem5b 42663 | Part 2 of Equation 1 of https://crypto.stanford.edu/pbc/notes/numberfield/fermatn4.html. (Contributed by SN, 22-Aug-2024.) |
| ⊢ 𝑀 = (((√‘(𝐶 + (𝐵↑2))) + (√‘(𝐶 − (𝐵↑2)))) / 2) & ⊢ 𝑁 = (((√‘(𝐶 + (𝐵↑2))) − (√‘(𝐶 − (𝐵↑2)))) / 2) & ⊢ 𝑅 = (((√‘(𝑀 + 𝑁)) + (√‘(𝑀 − 𝑁))) / 2) & ⊢ 𝑆 = (((√‘(𝑀 + 𝑁)) − (√‘(𝑀 − 𝑁))) / 2) & ⊢ (𝜑 → 𝐴 ∈ ℕ) & ⊢ (𝜑 → 𝐵 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ ℕ) & ⊢ (𝜑 → ¬ 2 ∥ 𝐴) & ⊢ (𝜑 → (𝐴 gcd 𝐶) = 1) & ⊢ (𝜑 → ((𝐴↑4) + (𝐵↑4)) = (𝐶↑2)) ⇒ ⊢ (𝜑 → (2 · (𝑀 · 𝑁)) = (𝐵↑2)) | ||
| Theorem | flt4lem5c 42664 | Part 2 of Equation 2 of https://crypto.stanford.edu/pbc/notes/numberfield/fermatn4.html. (Contributed by SN, 22-Aug-2024.) |
| ⊢ 𝑀 = (((√‘(𝐶 + (𝐵↑2))) + (√‘(𝐶 − (𝐵↑2)))) / 2) & ⊢ 𝑁 = (((√‘(𝐶 + (𝐵↑2))) − (√‘(𝐶 − (𝐵↑2)))) / 2) & ⊢ 𝑅 = (((√‘(𝑀 + 𝑁)) + (√‘(𝑀 − 𝑁))) / 2) & ⊢ 𝑆 = (((√‘(𝑀 + 𝑁)) − (√‘(𝑀 − 𝑁))) / 2) & ⊢ (𝜑 → 𝐴 ∈ ℕ) & ⊢ (𝜑 → 𝐵 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ ℕ) & ⊢ (𝜑 → ¬ 2 ∥ 𝐴) & ⊢ (𝜑 → (𝐴 gcd 𝐶) = 1) & ⊢ (𝜑 → ((𝐴↑4) + (𝐵↑4)) = (𝐶↑2)) ⇒ ⊢ (𝜑 → 𝑁 = (2 · (𝑅 · 𝑆))) | ||
| Theorem | flt4lem5d 42665 | Part 3 of Equation 2 of https://crypto.stanford.edu/pbc/notes/numberfield/fermatn4.html. (Contributed by SN, 23-Aug-2024.) |
| ⊢ 𝑀 = (((√‘(𝐶 + (𝐵↑2))) + (√‘(𝐶 − (𝐵↑2)))) / 2) & ⊢ 𝑁 = (((√‘(𝐶 + (𝐵↑2))) − (√‘(𝐶 − (𝐵↑2)))) / 2) & ⊢ 𝑅 = (((√‘(𝑀 + 𝑁)) + (√‘(𝑀 − 𝑁))) / 2) & ⊢ 𝑆 = (((√‘(𝑀 + 𝑁)) − (√‘(𝑀 − 𝑁))) / 2) & ⊢ (𝜑 → 𝐴 ∈ ℕ) & ⊢ (𝜑 → 𝐵 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ ℕ) & ⊢ (𝜑 → ¬ 2 ∥ 𝐴) & ⊢ (𝜑 → (𝐴 gcd 𝐶) = 1) & ⊢ (𝜑 → ((𝐴↑4) + (𝐵↑4)) = (𝐶↑2)) ⇒ ⊢ (𝜑 → 𝑀 = ((𝑅↑2) + (𝑆↑2))) | ||
| Theorem | flt4lem5e 42666 | Satisfy the hypotheses of flt4lem4 42659. (Contributed by SN, 23-Aug-2024.) |
| ⊢ 𝑀 = (((√‘(𝐶 + (𝐵↑2))) + (√‘(𝐶 − (𝐵↑2)))) / 2) & ⊢ 𝑁 = (((√‘(𝐶 + (𝐵↑2))) − (√‘(𝐶 − (𝐵↑2)))) / 2) & ⊢ 𝑅 = (((√‘(𝑀 + 𝑁)) + (√‘(𝑀 − 𝑁))) / 2) & ⊢ 𝑆 = (((√‘(𝑀 + 𝑁)) − (√‘(𝑀 − 𝑁))) / 2) & ⊢ (𝜑 → 𝐴 ∈ ℕ) & ⊢ (𝜑 → 𝐵 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ ℕ) & ⊢ (𝜑 → ¬ 2 ∥ 𝐴) & ⊢ (𝜑 → (𝐴 gcd 𝐶) = 1) & ⊢ (𝜑 → ((𝐴↑4) + (𝐵↑4)) = (𝐶↑2)) ⇒ ⊢ (𝜑 → (((𝑅 gcd 𝑆) = 1 ∧ (𝑅 gcd 𝑀) = 1 ∧ (𝑆 gcd 𝑀) = 1) ∧ (𝑅 ∈ ℕ ∧ 𝑆 ∈ ℕ ∧ 𝑀 ∈ ℕ) ∧ ((𝑀 · (𝑅 · 𝑆)) = ((𝐵 / 2)↑2) ∧ (𝐵 / 2) ∈ ℕ))) | ||
| Theorem | flt4lem5f 42667 | Final equation of https://crypto.stanford.edu/pbc/notes/numberfield/fermatn4.html. Given 𝐴↑4 + 𝐵↑4 = 𝐶↑2, provide a smaller solution. This satisfies the infinite descent condition. (Contributed by SN, 24-Aug-2024.) |
| ⊢ 𝑀 = (((√‘(𝐶 + (𝐵↑2))) + (√‘(𝐶 − (𝐵↑2)))) / 2) & ⊢ 𝑁 = (((√‘(𝐶 + (𝐵↑2))) − (√‘(𝐶 − (𝐵↑2)))) / 2) & ⊢ 𝑅 = (((√‘(𝑀 + 𝑁)) + (√‘(𝑀 − 𝑁))) / 2) & ⊢ 𝑆 = (((√‘(𝑀 + 𝑁)) − (√‘(𝑀 − 𝑁))) / 2) & ⊢ (𝜑 → 𝐴 ∈ ℕ) & ⊢ (𝜑 → 𝐵 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ ℕ) & ⊢ (𝜑 → ¬ 2 ∥ 𝐴) & ⊢ (𝜑 → (𝐴 gcd 𝐶) = 1) & ⊢ (𝜑 → ((𝐴↑4) + (𝐵↑4)) = (𝐶↑2)) ⇒ ⊢ (𝜑 → ((𝑀 gcd (𝐵 / 2))↑2) = (((𝑅 gcd (𝐵 / 2))↑4) + ((𝑆 gcd (𝐵 / 2))↑4))) | ||
| Theorem | flt4lem6 42668 | Remove shared factors in a solution to 𝐴↑4 + 𝐵↑4 = 𝐶↑2. (Contributed by SN, 24-Jul-2024.) |
| ⊢ (𝜑 → 𝐴 ∈ ℕ) & ⊢ (𝜑 → 𝐵 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ ℕ) & ⊢ (𝜑 → ((𝐴↑4) + (𝐵↑4)) = (𝐶↑2)) ⇒ ⊢ (𝜑 → (((𝐴 / (𝐴 gcd 𝐵)) ∈ ℕ ∧ (𝐵 / (𝐴 gcd 𝐵)) ∈ ℕ ∧ (𝐶 / ((𝐴 gcd 𝐵)↑2)) ∈ ℕ) ∧ (((𝐴 / (𝐴 gcd 𝐵))↑4) + ((𝐵 / (𝐴 gcd 𝐵))↑4)) = ((𝐶 / ((𝐴 gcd 𝐵)↑2))↑2))) | ||
| Theorem | flt4lem7 42669* | Convert flt4lem5f 42667 into a convenient form for nna4b4nsq 42670. TODO-SN: The change to (𝐴 gcd 𝐵) = 1 points at some inefficiency in the lemmas. (Contributed by SN, 25-Aug-2024.) |
| ⊢ (𝜑 → 𝐴 ∈ ℕ) & ⊢ (𝜑 → 𝐵 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ ℕ) & ⊢ (𝜑 → ¬ 2 ∥ 𝐴) & ⊢ (𝜑 → (𝐴 gcd 𝐵) = 1) & ⊢ (𝜑 → ((𝐴↑4) + (𝐵↑4)) = (𝐶↑2)) ⇒ ⊢ (𝜑 → ∃𝑙 ∈ ℕ (∃𝑔 ∈ ℕ ∃ℎ ∈ ℕ (¬ 2 ∥ 𝑔 ∧ ((𝑔 gcd ℎ) = 1 ∧ ((𝑔↑4) + (ℎ↑4)) = (𝑙↑2))) ∧ 𝑙 < 𝐶)) | ||
| Theorem | nna4b4nsq 42670 | Strengthening of Fermat's last theorem for exponent 4, where the sum is only assumed to be a square. (Contributed by SN, 23-Aug-2024.) |
| ⊢ (𝜑 → 𝐴 ∈ ℕ) & ⊢ (𝜑 → 𝐵 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ ℕ) ⇒ ⊢ (𝜑 → ((𝐴↑4) + (𝐵↑4)) ≠ (𝐶↑2)) | ||
| Theorem | fltltc 42671 | (𝐶↑𝑁) is the largest term and therefore 𝐵 < 𝐶. (Contributed by Steven Nguyen, 22-Aug-2023.) |
| ⊢ (𝜑 → 𝐴 ∈ ℕ) & ⊢ (𝜑 → 𝐵 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ ℕ) & ⊢ (𝜑 → 𝑁 ∈ (ℤ≥‘3)) & ⊢ (𝜑 → ((𝐴↑𝑁) + (𝐵↑𝑁)) = (𝐶↑𝑁)) ⇒ ⊢ (𝜑 → 𝐵 < 𝐶) | ||
| Theorem | fltnltalem 42672 | Lemma for fltnlta 42673. A lower bound for 𝐴 based on pwdif 15904. (Contributed by Steven Nguyen, 22-Aug-2023.) |
| ⊢ (𝜑 → 𝐴 ∈ ℕ) & ⊢ (𝜑 → 𝐵 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ ℕ) & ⊢ (𝜑 → 𝑁 ∈ (ℤ≥‘3)) & ⊢ (𝜑 → ((𝐴↑𝑁) + (𝐵↑𝑁)) = (𝐶↑𝑁)) ⇒ ⊢ (𝜑 → ((𝐶 − 𝐵) · ((𝐶↑(𝑁 − 1)) + ((𝑁 − 1) · (𝐵↑(𝑁 − 1))))) < (𝐴↑𝑁)) | ||
| Theorem | fltnlta 42673 | In a Fermat counterexample, the exponent 𝑁 is less than all three numbers (𝐴, 𝐵, and 𝐶). Note that 𝐴 < 𝐵 (hypothesis) and 𝐵 < 𝐶 (fltltc 42671). See https://youtu.be/EymVXkPWxyc 42671 for an outline. (Contributed by SN, 24-Aug-2023.) |
| ⊢ (𝜑 → 𝐴 ∈ ℕ) & ⊢ (𝜑 → 𝐵 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ ℕ) & ⊢ (𝜑 → 𝑁 ∈ (ℤ≥‘3)) & ⊢ (𝜑 → ((𝐴↑𝑁) + (𝐵↑𝑁)) = (𝐶↑𝑁)) & ⊢ (𝜑 → 𝐴 < 𝐵) ⇒ ⊢ (𝜑 → 𝑁 < 𝐴) | ||
These theorems were added for illustration or pedagogical purposes without the intention of being used, but some may still be moved to main and used, of course. | ||
| Theorem | iddii 42674 | Version of a1ii 2 with the hypotheses switched. The first hypothesis is redundant so this theorem should not normally appear in a proof. Inference associated with idd 24. (Contributed by SN, 1-Apr-2025.) (New usage is discouraged.) |
| ⊢ 𝜑 & ⊢ 𝜓 ⇒ ⊢ 𝜓 | ||
| Theorem | bicomdALT 42675 | Alternate proof of bicomd 223 which is shorter after expanding all parent theorems (as of 8-Aug-2024, bicom 222 depends on bicom1 221 and sylib 218 depends on syl 17). Additionally, the labels bicom1 221 and syl 17 happen to contain fewer characters than bicom 222 and sylib 218. However, neither of these conditions count as a shortening according to conventions 30419. In the first case, the criteria could easily be broken by upstream changes, and in many cases the upstream dependency tree is nontrivial (see orass 922 and pm2.31 923). For the latter case, theorem labels are up to revision, so they are not counted in the size of a proof. (Contributed by SN, 21-May-2022.) (New usage is discouraged.) (Proof modification is discouraged.) |
| ⊢ (𝜑 → (𝜓 ↔ 𝜒)) ⇒ ⊢ (𝜑 → (𝜒 ↔ 𝜓)) | ||
| Theorem | alan 42676 | Alias for 19.26 1870 for easier lookup. (Contributed by SN, 12-Aug-2025.) (New usage is discouraged.) |
| ⊢ (∀𝑥(𝜑 ∧ 𝜓) ↔ (∀𝑥𝜑 ∧ ∀𝑥𝜓)) | ||
| Theorem | exor 42677 | Alias for 19.43 1882 for easier lookup. (Contributed by SN, 5-Jul-2025.) (New usage is discouraged.) |
| ⊢ (∃𝑥(𝜑 ∨ 𝜓) ↔ (∃𝑥𝜑 ∨ ∃𝑥𝜓)) | ||
| Theorem | rexor 42678 | Alias for r19.43 3122 for easier lookup. (Contributed by SN, 5-Jul-2025.) (New usage is discouraged.) |
| ⊢ (∃𝑥 ∈ 𝐴 (𝜑 ∨ 𝜓) ↔ (∃𝑥 ∈ 𝐴 𝜑 ∨ ∃𝑥 ∈ 𝐴 𝜓)) | ||
| Theorem | ruvALT 42679 | Alternate proof of ruv 9642 with one fewer syntax step thanks to using elirrv 9636 instead of elirr 9637. However, it does not change the compressed proof size or the number of symbols in the generated display, so it is not considered a shortening according to conventions 30419. (Contributed by SN, 1-Sep-2024.) (New usage is discouraged.) (Proof modification is discouraged.) |
| ⊢ {𝑥 ∣ 𝑥 ∉ 𝑥} = V | ||
| Theorem | sn-wcdeq 42680 | Alternative to wcdeq 3769 and df-cdeq 3770. This flattens the syntax representation ( wi ( weq vx vy ) wph ) to ( sn-wcdeq vx vy wph ), illustrating the comment of df-cdeq 3770. (Contributed by SN, 26-Sep-2024.) (New usage is discouraged.) |
| wff (𝑥 = 𝑦 → 𝜑) | ||
| Theorem | sq45 42681 | 45 squared is 2025. (Contributed by SN, 30-Mar-2025.) |
| ⊢ (;45↑2) = ;;;2025 | ||
| Theorem | sum9cubes 42682 | The sum of the first nine perfect cubes is 2025. (Contributed by SN, 30-Mar-2025.) |
| ⊢ Σ𝑘 ∈ (1...9)(𝑘↑3) = ;;;2025 | ||
| Theorem | sn-isghm 42683* | Longer proof of isghm 19233, unsuccessfully attempting to simplify isghm 19233 using elovmpo 7678 according to an editorial note (now removed). (Contributed by SN, 7-Jun-2025.) (Proof modification is discouraged.) (New usage is discouraged.) |
| ⊢ 𝑋 = (Base‘𝑆) & ⊢ 𝑌 = (Base‘𝑇) & ⊢ + = (+g‘𝑆) & ⊢ ⨣ = (+g‘𝑇) ⇒ ⊢ (𝐹 ∈ (𝑆 GrpHom 𝑇) ↔ ((𝑆 ∈ Grp ∧ 𝑇 ∈ Grp) ∧ (𝐹:𝑋⟶𝑌 ∧ ∀𝑢 ∈ 𝑋 ∀𝑣 ∈ 𝑋 (𝐹‘(𝑢 + 𝑣)) = ((𝐹‘𝑢) ⨣ (𝐹‘𝑣))))) | ||
| Theorem | aprilfools2025 42684 | An abuse of notation. (Contributed by Prof. Loof Lirpa, 1-Apr-2025.) (New usage is discouraged.) (Proof modification is discouraged.) |
| ⊢ {〈“𝐴𝑝𝑟𝑖𝑙”〉, 〈“𝑓𝑜𝑜𝑙𝑠!”〉} ∈ V | ||
It is known that ax-10 2141, ax-11 2157, and ax-12 2177 are logically redundant in a weak sense. Practically, they can be replaced with hbn1w 2046, alcomimw 2042, and ax12wlem 2132 as long as you can fully substitute 𝑦 for 𝑥 in the relevant wff (that is, 𝑥 cannot appear in the wff after substituting). This strategy (which I will call a "standard replacement" of axioms) has a lot of potential, for example it works with df-fv 6569 and df-mpt 5226, two very common constructions. But doing a standard replacement of ax-10 2141, ax-11 2157, and ax-12 2177 takes unsatisfyingly long. Usually, if another approach is found, that approach is shorter and better. | ||
| Theorem | nfa1w 42685* | Replace ax-10 2141 in nfa1 2151 with a substitution hypothesis. (Contributed by SN, 2-Sep-2025.) |
| ⊢ (𝑥 = 𝑦 → (𝜑 ↔ 𝜓)) ⇒ ⊢ Ⅎ𝑥∀𝑥𝜑 | ||
| Theorem | eu6w 42686* | Replace ax-10 2141, ax-12 2177 in eu6 2574 with substitution hypotheses. (Contributed by SN, 27-May-2025.) |
| ⊢ (𝑥 = 𝑧 → (𝜑 ↔ 𝜓)) & ⊢ (𝑥 = 𝑦 → (𝜑 ↔ 𝜃)) ⇒ ⊢ (∃!𝑥𝜑 ↔ ∃𝑦∀𝑥(𝜑 ↔ 𝑥 = 𝑦)) | ||
| Theorem | abbibw 42687* | Replace ax-10 2141, ax-11 2157, ax-12 2177 in abbib 2811 with substitution hypotheses. (Contributed by SN, 27-May-2025.) |
| ⊢ (𝑥 = 𝑦 → (𝜑 ↔ 𝜃)) & ⊢ (𝑥 = 𝑦 → (𝜓 ↔ 𝜒)) ⇒ ⊢ ({𝑥 ∣ 𝜑} = {𝑥 ∣ 𝜓} ↔ ∀𝑥(𝜑 ↔ 𝜓)) | ||
| Theorem | absnw 42688* | Replace ax-10 2141, ax-11 2157, ax-12 2177 in absn 4645 with a substitution hypothesis. (Contributed by SN, 27-May-2025.) |
| ⊢ (𝑥 = 𝑦 → (𝜑 ↔ 𝜓)) ⇒ ⊢ ({𝑥 ∣ 𝜑} = {𝑌} ↔ ∀𝑥(𝜑 ↔ 𝑥 = 𝑌)) | ||
| Theorem | euabsn2w 42689* | Replace ax-10 2141, ax-11 2157, ax-12 2177 in euabsn2 4725 with substitution hypotheses. (Contributed by SN, 27-May-2025.) |
| ⊢ (𝑥 = 𝑦 → (𝜑 ↔ 𝜓)) & ⊢ (𝑥 = 𝑧 → (𝜑 ↔ 𝜃)) ⇒ ⊢ (∃!𝑥𝜑 ↔ ∃𝑦{𝑥 ∣ 𝜑} = {𝑦}) | ||
| Theorem | sn-tz6.12-2 42690* | tz6.12-2 6894 without ax-10 2141, ax-11 2157, ax-12 2177. Improves 118 theorems. (Contributed by SN, 27-May-2025.) |
| ⊢ (¬ ∃!𝑥 𝐴𝐹𝑥 → (𝐹‘𝐴) = ∅) | ||
| Theorem | cu3addd 42691 | Cube of sum of three numbers. (Contributed by Igor Ieskov, 14-Dec-2023.) |
| ⊢ (𝜑 → 𝐴 ∈ ℂ) & ⊢ (𝜑 → 𝐵 ∈ ℂ) & ⊢ (𝜑 → 𝐶 ∈ ℂ) ⇒ ⊢ (𝜑 → (((𝐴 + 𝐵) + 𝐶)↑3) = (((((𝐴↑3) + (3 · ((𝐴↑2) · 𝐵))) + ((3 · (𝐴 · (𝐵↑2))) + (𝐵↑3))) + (((3 · ((𝐴↑2) · 𝐶)) + (((3 · 2) · (𝐴 · 𝐵)) · 𝐶)) + (3 · ((𝐵↑2) · 𝐶)))) + (((3 · (𝐴 · (𝐶↑2))) + (3 · (𝐵 · (𝐶↑2)))) + (𝐶↑3)))) | ||
| Theorem | sqnegd 42692 | The square of the negative of a number. (Contributed by Igor Ieskov, 21-Jan-2024.) |
| ⊢ (𝜑 → 𝐴 ∈ ℂ) ⇒ ⊢ (𝜑 → (-𝐴↑2) = (𝐴↑2)) | ||
| Theorem | negexpidd 42693 | The sum of a real number to the power of N and the negative of the number to the power of N equals zero if N is a nonnegative odd integer. (Contributed by Igor Ieskov, 21-Jan-2024.) |
| ⊢ (𝜑 → 𝐴 ∈ ℝ) & ⊢ (𝜑 → 𝑁 ∈ ℕ0) & ⊢ (𝜑 → ¬ 2 ∥ 𝑁) ⇒ ⊢ (𝜑 → ((𝐴↑𝑁) + (-𝐴↑𝑁)) = 0) | ||
| Theorem | rexlimdv3d 42694* | An extended version of rexlimdvv 3212 to include three set variables. (Contributed by Igor Ieskov, 21-Jan-2024.) |
| ⊢ (𝜑 → ((𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵 ∧ 𝑧 ∈ 𝐶) → (𝜓 → 𝜒))) ⇒ ⊢ (𝜑 → (∃𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝐵 ∃𝑧 ∈ 𝐶 𝜓 → 𝜒)) | ||
| Theorem | 3cubeslem1 42695 | Lemma for 3cubes 42701. (Contributed by Igor Ieskov, 22-Jan-2024.) |
| ⊢ (𝜑 → 𝐴 ∈ ℚ) ⇒ ⊢ (𝜑 → 0 < (((𝐴 + 1)↑2) − 𝐴)) | ||
| Theorem | 3cubeslem2 42696 | Lemma for 3cubes 42701. Used to show that the denominators in 3cubeslem4 42700 are nonzero. (Contributed by Igor Ieskov, 22-Jan-2024.) |
| ⊢ (𝜑 → 𝐴 ∈ ℚ) ⇒ ⊢ (𝜑 → ¬ ((((3↑3) · (𝐴↑2)) + ((3↑2) · 𝐴)) + 3) = 0) | ||
| Theorem | 3cubeslem3l 42697 | Lemma for 3cubes 42701. (Contributed by Igor Ieskov, 22-Jan-2024.) |
| ⊢ (𝜑 → 𝐴 ∈ ℚ) ⇒ ⊢ (𝜑 → (𝐴 · (((((3↑3) · (𝐴↑2)) + ((3↑2) · 𝐴)) + 3)↑3)) = (((𝐴↑7) · (3↑9)) + (((𝐴↑6) · (3↑9)) + (((𝐴↑5) · ((3↑8) + (3↑8))) + (((𝐴↑4) · (((3↑7) · 2) + (3↑6))) + (((𝐴↑3) · ((3↑6) + (3↑6))) + (((𝐴↑2) · (3↑5)) + (𝐴 · (3↑3))))))))) | ||
| Theorem | 3cubeslem3r 42698 | Lemma for 3cubes 42701. (Contributed by Igor Ieskov, 22-Jan-2024.) |
| ⊢ (𝜑 → 𝐴 ∈ ℚ) ⇒ ⊢ (𝜑 → ((((((3↑3) · (𝐴↑3)) − 1)↑3) + (((-((3↑3) · (𝐴↑3)) + ((3↑2) · 𝐴)) + 1)↑3)) + ((((3↑3) · (𝐴↑2)) + ((3↑2) · 𝐴))↑3)) = (((𝐴↑7) · (3↑9)) + (((𝐴↑6) · (3↑9)) + (((𝐴↑5) · ((3↑8) + (3↑8))) + (((𝐴↑4) · (((3↑7) · 2) + (3↑6))) + (((𝐴↑3) · ((3↑6) + (3↑6))) + (((𝐴↑2) · (3↑5)) + (𝐴 · (3↑3))))))))) | ||
| Theorem | 3cubeslem3 42699 | Lemma for 3cubes 42701. (Contributed by Igor Ieskov, 22-Jan-2024.) |
| ⊢ (𝜑 → 𝐴 ∈ ℚ) ⇒ ⊢ (𝜑 → (𝐴 · (((((3↑3) · (𝐴↑2)) + ((3↑2) · 𝐴)) + 3)↑3)) = ((((((3↑3) · (𝐴↑3)) − 1)↑3) + (((-((3↑3) · (𝐴↑3)) + ((3↑2) · 𝐴)) + 1)↑3)) + ((((3↑3) · (𝐴↑2)) + ((3↑2) · 𝐴))↑3))) | ||
| Theorem | 3cubeslem4 42700 | Lemma for 3cubes 42701. This is Ryley's explicit formula for decomposing a rational 𝐴 into a sum of three rational cubes. (Contributed by Igor Ieskov, 22-Jan-2024.) |
| ⊢ (𝜑 → 𝐴 ∈ ℚ) ⇒ ⊢ (𝜑 → 𝐴 = (((((((3↑3) · (𝐴↑3)) − 1) / ((((3↑3) · (𝐴↑2)) + ((3↑2) · 𝐴)) + 3))↑3) + ((((-((3↑3) · (𝐴↑3)) + ((3↑2) · 𝐴)) + 1) / ((((3↑3) · (𝐴↑2)) + ((3↑2) · 𝐴)) + 3))↑3)) + (((((3↑3) · (𝐴↑2)) + ((3↑2) · 𝐴)) / ((((3↑3) · (𝐴↑2)) + ((3↑2) · 𝐴)) + 3))↑3))) | ||
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