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Type | Label | Description |
---|---|---|
Statement | ||
Theorem | supmullem2 11601* | Lemma for supmul 11602. (Contributed by Mario Carneiro, 5-Jul-2013.) |
⊢ 𝐶 = {𝑧 ∣ ∃𝑣 ∈ 𝐴 ∃𝑏 ∈ 𝐵 𝑧 = (𝑣 · 𝑏)} & ⊢ (𝜑 ↔ ((∀𝑥 ∈ 𝐴 0 ≤ 𝑥 ∧ ∀𝑥 ∈ 𝐵 0 ≤ 𝑥) ∧ (𝐴 ⊆ ℝ ∧ 𝐴 ≠ ∅ ∧ ∃𝑥 ∈ ℝ ∀𝑦 ∈ 𝐴 𝑦 ≤ 𝑥) ∧ (𝐵 ⊆ ℝ ∧ 𝐵 ≠ ∅ ∧ ∃𝑥 ∈ ℝ ∀𝑦 ∈ 𝐵 𝑦 ≤ 𝑥))) ⇒ ⊢ (𝜑 → (𝐶 ⊆ ℝ ∧ 𝐶 ≠ ∅ ∧ ∃𝑥 ∈ ℝ ∀𝑤 ∈ 𝐶 𝑤 ≤ 𝑥)) | ||
Theorem | supmul 11602* | The supremum function distributes over multiplication, in the sense that (sup𝐴) · (sup𝐵) = sup(𝐴 · 𝐵), where 𝐴 · 𝐵 is shorthand for {𝑎 · 𝑏 ∣ 𝑎 ∈ 𝐴, 𝑏 ∈ 𝐵} and is defined as 𝐶 below. We made use of this in our definition of multiplication in the Dedekind cut construction of the reals (see df-mp 10395). (Contributed by Mario Carneiro, 5-Jul-2013.) (Revised by Mario Carneiro, 6-Sep-2014.) |
⊢ 𝐶 = {𝑧 ∣ ∃𝑣 ∈ 𝐴 ∃𝑏 ∈ 𝐵 𝑧 = (𝑣 · 𝑏)} & ⊢ (𝜑 ↔ ((∀𝑥 ∈ 𝐴 0 ≤ 𝑥 ∧ ∀𝑥 ∈ 𝐵 0 ≤ 𝑥) ∧ (𝐴 ⊆ ℝ ∧ 𝐴 ≠ ∅ ∧ ∃𝑥 ∈ ℝ ∀𝑦 ∈ 𝐴 𝑦 ≤ 𝑥) ∧ (𝐵 ⊆ ℝ ∧ 𝐵 ≠ ∅ ∧ ∃𝑥 ∈ ℝ ∀𝑦 ∈ 𝐵 𝑦 ≤ 𝑥))) ⇒ ⊢ (𝜑 → (sup(𝐴, ℝ, < ) · sup(𝐵, ℝ, < )) = sup(𝐶, ℝ, < )) | ||
Theorem | sup3ii 11603* | A version of the completeness axiom for reals. (Contributed by NM, 23-Aug-1999.) |
⊢ (𝐴 ⊆ ℝ ∧ 𝐴 ≠ ∅ ∧ ∃𝑥 ∈ ℝ ∀𝑦 ∈ 𝐴 𝑦 ≤ 𝑥) ⇒ ⊢ ∃𝑥 ∈ ℝ (∀𝑦 ∈ 𝐴 ¬ 𝑥 < 𝑦 ∧ ∀𝑦 ∈ ℝ (𝑦 < 𝑥 → ∃𝑧 ∈ 𝐴 𝑦 < 𝑧)) | ||
Theorem | suprclii 11604* | Closure of supremum of a nonempty bounded set of reals. (Contributed by NM, 12-Sep-1999.) |
⊢ (𝐴 ⊆ ℝ ∧ 𝐴 ≠ ∅ ∧ ∃𝑥 ∈ ℝ ∀𝑦 ∈ 𝐴 𝑦 ≤ 𝑥) ⇒ ⊢ sup(𝐴, ℝ, < ) ∈ ℝ | ||
Theorem | suprubii 11605* | A member of a nonempty bounded set of reals is less than or equal to the set's upper bound. (Contributed by NM, 12-Sep-1999.) |
⊢ (𝐴 ⊆ ℝ ∧ 𝐴 ≠ ∅ ∧ ∃𝑥 ∈ ℝ ∀𝑦 ∈ 𝐴 𝑦 ≤ 𝑥) ⇒ ⊢ (𝐵 ∈ 𝐴 → 𝐵 ≤ sup(𝐴, ℝ, < )) | ||
Theorem | suprlubii 11606* | The supremum of a nonempty bounded set of reals is the least upper bound. (Contributed by NM, 15-Oct-2004.) (Revised by Mario Carneiro, 6-Sep-2014.) |
⊢ (𝐴 ⊆ ℝ ∧ 𝐴 ≠ ∅ ∧ ∃𝑥 ∈ ℝ ∀𝑦 ∈ 𝐴 𝑦 ≤ 𝑥) ⇒ ⊢ (𝐵 ∈ ℝ → (𝐵 < sup(𝐴, ℝ, < ) ↔ ∃𝑧 ∈ 𝐴 𝐵 < 𝑧)) | ||
Theorem | suprnubii 11607* | An upper bound is not less than the supremum of a nonempty bounded set of reals. (Contributed by NM, 15-Oct-2004.) (Revised by Mario Carneiro, 6-Sep-2014.) |
⊢ (𝐴 ⊆ ℝ ∧ 𝐴 ≠ ∅ ∧ ∃𝑥 ∈ ℝ ∀𝑦 ∈ 𝐴 𝑦 ≤ 𝑥) ⇒ ⊢ (𝐵 ∈ ℝ → (¬ 𝐵 < sup(𝐴, ℝ, < ) ↔ ∀𝑧 ∈ 𝐴 ¬ 𝐵 < 𝑧)) | ||
Theorem | suprleubii 11608* | The supremum of a nonempty bounded set of reals is less than or equal to an upper bound. (Contributed by NM, 18-Mar-2005.) (Revised by Mario Carneiro, 6-Sep-2014.) |
⊢ (𝐴 ⊆ ℝ ∧ 𝐴 ≠ ∅ ∧ ∃𝑥 ∈ ℝ ∀𝑦 ∈ 𝐴 𝑦 ≤ 𝑥) ⇒ ⊢ (𝐵 ∈ ℝ → (sup(𝐴, ℝ, < ) ≤ 𝐵 ↔ ∀𝑧 ∈ 𝐴 𝑧 ≤ 𝐵)) | ||
Theorem | riotaneg 11609* | The negative of the unique real such that 𝜑. (Contributed by NM, 13-Jun-2005.) |
⊢ (𝑥 = -𝑦 → (𝜑 ↔ 𝜓)) ⇒ ⊢ (∃!𝑥 ∈ ℝ 𝜑 → (℩𝑥 ∈ ℝ 𝜑) = -(℩𝑦 ∈ ℝ 𝜓)) | ||
Theorem | negiso 11610 | Negation is an order anti-isomorphism of the real numbers, which is its own inverse. (Contributed by Mario Carneiro, 24-Dec-2016.) |
⊢ 𝐹 = (𝑥 ∈ ℝ ↦ -𝑥) ⇒ ⊢ (𝐹 Isom < , ◡ < (ℝ, ℝ) ∧ ◡𝐹 = 𝐹) | ||
Theorem | dfinfre 11611* | The infimum of a set of reals 𝐴. (Contributed by NM, 9-Oct-2005.) (Revised by AV, 4-Sep-2020.) |
⊢ (𝐴 ⊆ ℝ → inf(𝐴, ℝ, < ) = ∪ {𝑥 ∈ ℝ ∣ (∀𝑦 ∈ 𝐴 𝑥 ≤ 𝑦 ∧ ∀𝑦 ∈ ℝ (𝑥 < 𝑦 → ∃𝑧 ∈ 𝐴 𝑧 < 𝑦))}) | ||
Theorem | infrecl 11612* | Closure of infimum of a nonempty bounded set of reals. (Contributed by NM, 8-Oct-2005.) (Revised by AV, 4-Sep-2020.) |
⊢ ((𝐴 ⊆ ℝ ∧ 𝐴 ≠ ∅ ∧ ∃𝑥 ∈ ℝ ∀𝑦 ∈ 𝐴 𝑥 ≤ 𝑦) → inf(𝐴, ℝ, < ) ∈ ℝ) | ||
Theorem | infrenegsup 11613* | The infimum of a set of reals 𝐴 is the negative of the supremum of the negatives of its elements. The antecedent ensures that 𝐴 is nonempty and has a lower bound. (Contributed by NM, 14-Jun-2005.) (Revised by AV, 4-Sep-2020.) |
⊢ ((𝐴 ⊆ ℝ ∧ 𝐴 ≠ ∅ ∧ ∃𝑥 ∈ ℝ ∀𝑦 ∈ 𝐴 𝑥 ≤ 𝑦) → inf(𝐴, ℝ, < ) = -sup({𝑧 ∈ ℝ ∣ -𝑧 ∈ 𝐴}, ℝ, < )) | ||
Theorem | infregelb 11614* | Any lower bound of a nonempty set of real numbers is less than or equal to its infimum. (Contributed by Jeff Hankins, 1-Sep-2013.) (Revised by AV, 4-Sep-2020.) (Proof modification is discouraged.) |
⊢ (((𝐴 ⊆ ℝ ∧ 𝐴 ≠ ∅ ∧ ∃𝑥 ∈ ℝ ∀𝑦 ∈ 𝐴 𝑥 ≤ 𝑦) ∧ 𝐵 ∈ ℝ) → (𝐵 ≤ inf(𝐴, ℝ, < ) ↔ ∀𝑧 ∈ 𝐴 𝐵 ≤ 𝑧)) | ||
Theorem | infrelb 11615* | If a nonempty set of real numbers has a lower bound, its infimum is less than or equal to any of its elements. (Contributed by Jeff Hankins, 15-Sep-2013.) (Revised by AV, 4-Sep-2020.) |
⊢ ((𝐵 ⊆ ℝ ∧ ∃𝑥 ∈ ℝ ∀𝑦 ∈ 𝐵 𝑥 ≤ 𝑦 ∧ 𝐴 ∈ 𝐵) → inf(𝐵, ℝ, < ) ≤ 𝐴) | ||
Theorem | supfirege 11616 | The supremum of a finite set of real numbers is greater than or equal to all the real numbers of the set. (Contributed by AV, 1-Oct-2019.) |
⊢ (𝜑 → 𝐵 ⊆ ℝ) & ⊢ (𝜑 → 𝐵 ∈ Fin) & ⊢ (𝜑 → 𝐶 ∈ 𝐵) & ⊢ (𝜑 → 𝑆 = sup(𝐵, ℝ, < )) ⇒ ⊢ (𝜑 → 𝐶 ≤ 𝑆) | ||
Theorem | inelr 11617 | The imaginary unit i is not a real number. (Contributed by NM, 6-May-1999.) |
⊢ ¬ i ∈ ℝ | ||
Theorem | rimul 11618 | A real number times the imaginary unit is real only if the number is 0. (Contributed by NM, 28-May-1999.) (Revised by Mario Carneiro, 27-May-2016.) |
⊢ ((𝐴 ∈ ℝ ∧ (i · 𝐴) ∈ ℝ) → 𝐴 = 0) | ||
Theorem | cru 11619 | The representation of complex numbers in terms of real and imaginary parts is unique. Proposition 10-1.3 of [Gleason] p. 130. (Contributed by NM, 9-May-1999.) (Proof shortened by Mario Carneiro, 27-May-2016.) |
⊢ (((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ) ∧ (𝐶 ∈ ℝ ∧ 𝐷 ∈ ℝ)) → ((𝐴 + (i · 𝐵)) = (𝐶 + (i · 𝐷)) ↔ (𝐴 = 𝐶 ∧ 𝐵 = 𝐷))) | ||
Theorem | crne0 11620 | The real representation of complex numbers is nonzero iff one of its terms is nonzero. (Contributed by NM, 29-Apr-2005.) (Proof shortened by Mario Carneiro, 27-May-2016.) |
⊢ ((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ) → ((𝐴 ≠ 0 ∨ 𝐵 ≠ 0) ↔ (𝐴 + (i · 𝐵)) ≠ 0)) | ||
Theorem | creur 11621* | The real part of a complex number is unique. Proposition 10-1.3 of [Gleason] p. 130. (Contributed by NM, 9-May-1999.) (Proof shortened by Mario Carneiro, 27-May-2016.) |
⊢ (𝐴 ∈ ℂ → ∃!𝑥 ∈ ℝ ∃𝑦 ∈ ℝ 𝐴 = (𝑥 + (i · 𝑦))) | ||
Theorem | creui 11622* | The imaginary part of a complex number is unique. Proposition 10-1.3 of [Gleason] p. 130. (Contributed by NM, 9-May-1999.) (Proof shortened by Mario Carneiro, 27-May-2016.) |
⊢ (𝐴 ∈ ℂ → ∃!𝑦 ∈ ℝ ∃𝑥 ∈ ℝ 𝐴 = (𝑥 + (i · 𝑦))) | ||
Theorem | cju 11623* | The complex conjugate of a complex number is unique. (Contributed by Mario Carneiro, 6-Nov-2013.) |
⊢ (𝐴 ∈ ℂ → ∃!𝑥 ∈ ℂ ((𝐴 + 𝑥) ∈ ℝ ∧ (i · (𝐴 − 𝑥)) ∈ ℝ)) | ||
Theorem | ofsubeq0 11624 | Function analogue of subeq0 10901. (Contributed by Mario Carneiro, 24-Jul-2014.) |
⊢ ((𝐴 ∈ 𝑉 ∧ 𝐹:𝐴⟶ℂ ∧ 𝐺:𝐴⟶ℂ) → ((𝐹 ∘f − 𝐺) = (𝐴 × {0}) ↔ 𝐹 = 𝐺)) | ||
Theorem | ofnegsub 11625 | Function analogue of negsub 10923. (Contributed by Mario Carneiro, 24-Jul-2014.) |
⊢ ((𝐴 ∈ 𝑉 ∧ 𝐹:𝐴⟶ℂ ∧ 𝐺:𝐴⟶ℂ) → (𝐹 ∘f + ((𝐴 × {-1}) ∘f · 𝐺)) = (𝐹 ∘f − 𝐺)) | ||
Theorem | ofsubge0 11626 | Function analogue of subge0 11142. (Contributed by Mario Carneiro, 24-Jul-2014.) |
⊢ ((𝐴 ∈ 𝑉 ∧ 𝐹:𝐴⟶ℝ ∧ 𝐺:𝐴⟶ℝ) → ((𝐴 × {0}) ∘r ≤ (𝐹 ∘f − 𝐺) ↔ 𝐺 ∘r ≤ 𝐹)) | ||
Syntax | cn 11627 | Extend class notation to include the class of positive integers. |
class ℕ | ||
Definition | df-nn 11628 |
Define the set of positive integers. Some authors, especially in analysis
books, call these the natural numbers, whereas other authors choose to
include 0 in their definition of natural numbers. Note that ℕ is a
subset of complex numbers (nnsscn 11632), in contrast to the more elementary
ordinal natural numbers ω, df-om 7569). See nnind 11645 for the
principle of mathematical induction. See df-n0 11887 for the set of
nonnegative integers ℕ0. See dfn2 11899
for ℕ defined in terms of
ℕ0.
This is a technical definition that helps us avoid the Axiom of Infinity ax-inf2 9093 in certain proofs. For a more conventional and intuitive definition ("the smallest set of reals containing 1 as well as the successor of every member") see dfnn3 11641 (or its slight variant dfnn2 11640). (Contributed by NM, 10-Jan-1997.) (Revised by Mario Carneiro, 3-May-2014.) |
⊢ ℕ = (rec((𝑥 ∈ V ↦ (𝑥 + 1)), 1) “ ω) | ||
Theorem | nnexALT 11629 | Alternate proof of nnex 11633, more direct, that makes use of ax-rep 5182. (Contributed by Mario Carneiro, 3-May-2014.) (Proof modification is discouraged.) (New usage is discouraged.) |
⊢ ℕ ∈ V | ||
Theorem | peano5nni 11630* | Peano's inductive postulate. Theorem I.36 (principle of mathematical induction) of [Apostol] p. 34. (Contributed by NM, 10-Jan-1997.) (Revised by Mario Carneiro, 17-Nov-2014.) |
⊢ ((1 ∈ 𝐴 ∧ ∀𝑥 ∈ 𝐴 (𝑥 + 1) ∈ 𝐴) → ℕ ⊆ 𝐴) | ||
Theorem | nnssre 11631 | The positive integers are a subset of the reals. (Contributed by NM, 10-Jan-1997.) (Revised by Mario Carneiro, 16-Jun-2013.) |
⊢ ℕ ⊆ ℝ | ||
Theorem | nnsscn 11632 | The positive integers are a subset of the complex numbers. Remark: this could also be proven from nnssre 11631 and ax-resscn 10583 at the cost of using more axioms. (Contributed by NM, 2-Aug-2004.) Reduce dependencies on axioms. (Revised by Steven Nguyen, 4-Oct-2022.) |
⊢ ℕ ⊆ ℂ | ||
Theorem | nnex 11633 | The set of positive integers exists. (Contributed by NM, 3-Oct-1999.) (Revised by Mario Carneiro, 17-Nov-2014.) |
⊢ ℕ ∈ V | ||
Theorem | nnre 11634 | A positive integer is a real number. (Contributed by NM, 18-Aug-1999.) |
⊢ (𝐴 ∈ ℕ → 𝐴 ∈ ℝ) | ||
Theorem | nncn 11635 | A positive integer is a complex number. (Contributed by NM, 18-Aug-1999.) |
⊢ (𝐴 ∈ ℕ → 𝐴 ∈ ℂ) | ||
Theorem | nnrei 11636 | A positive integer is a real number. (Contributed by NM, 18-Aug-1999.) |
⊢ 𝐴 ∈ ℕ ⇒ ⊢ 𝐴 ∈ ℝ | ||
Theorem | nncni 11637 | A positive integer is a complex number. (Contributed by NM, 18-Aug-1999.) Reduce dependencies on axioms. (Revised by Steven Nguyen, 4-Oct-2022.) |
⊢ 𝐴 ∈ ℕ ⇒ ⊢ 𝐴 ∈ ℂ | ||
Theorem | 1nn 11638 | Peano postulate: 1 is a positive integer. (Contributed by NM, 11-Jan-1997.) (Revised by Mario Carneiro, 17-Nov-2014.) |
⊢ 1 ∈ ℕ | ||
Theorem | peano2nn 11639 | Peano postulate: a successor of a positive integer is a positive integer. (Contributed by NM, 11-Jan-1997.) (Revised by Mario Carneiro, 17-Nov-2014.) |
⊢ (𝐴 ∈ ℕ → (𝐴 + 1) ∈ ℕ) | ||
Theorem | dfnn2 11640* | Alternate definition of the set of positive integers. This was our original definition, before the current df-nn 11628 replaced it. This definition requires the axiom of infinity to ensure it has the properties we expect. (Contributed by Jeff Hankins, 12-Sep-2013.) (Revised by Mario Carneiro, 3-May-2014.) |
⊢ ℕ = ∩ {𝑥 ∣ (1 ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 (𝑦 + 1) ∈ 𝑥)} | ||
Theorem | dfnn3 11641* | Alternate definition of the set of positive integers. Definition of positive integers in [Apostol] p. 22. (Contributed by NM, 3-Jul-2005.) |
⊢ ℕ = ∩ {𝑥 ∣ (𝑥 ⊆ ℝ ∧ 1 ∈ 𝑥 ∧ ∀𝑦 ∈ 𝑥 (𝑦 + 1) ∈ 𝑥)} | ||
Theorem | nnred 11642 | A positive integer is a real number. (Contributed by Mario Carneiro, 27-May-2016.) |
⊢ (𝜑 → 𝐴 ∈ ℕ) ⇒ ⊢ (𝜑 → 𝐴 ∈ ℝ) | ||
Theorem | nncnd 11643 | A positive integer is a complex number. (Contributed by Mario Carneiro, 27-May-2016.) |
⊢ (𝜑 → 𝐴 ∈ ℕ) ⇒ ⊢ (𝜑 → 𝐴 ∈ ℂ) | ||
Theorem | peano2nnd 11644 | Peano postulate: a successor of a positive integer is a positive integer. (Contributed by Mario Carneiro, 27-May-2016.) |
⊢ (𝜑 → 𝐴 ∈ ℕ) ⇒ ⊢ (𝜑 → (𝐴 + 1) ∈ ℕ) | ||
Theorem | nnind 11645* | Principle of Mathematical Induction (inference schema). The first four hypotheses give us the substitution instances we need; the last two are the basis and the induction step. See nnaddcl 11649 for an example of its use. See nn0ind 12066 for induction on nonnegative integers and uzind 12063, uzind4 12295 for induction on an arbitrary upper set of integers. See indstr 12305 for strong induction. See also nnindALT 11646. This is an alternative for Metamath 100 proof #74. (Contributed by NM, 10-Jan-1997.) (Revised by Mario Carneiro, 16-Jun-2013.) |
⊢ (𝑥 = 1 → (𝜑 ↔ 𝜓)) & ⊢ (𝑥 = 𝑦 → (𝜑 ↔ 𝜒)) & ⊢ (𝑥 = (𝑦 + 1) → (𝜑 ↔ 𝜃)) & ⊢ (𝑥 = 𝐴 → (𝜑 ↔ 𝜏)) & ⊢ 𝜓 & ⊢ (𝑦 ∈ ℕ → (𝜒 → 𝜃)) ⇒ ⊢ (𝐴 ∈ ℕ → 𝜏) | ||
Theorem | nnindALT 11646* |
Principle of Mathematical Induction (inference schema). The last four
hypotheses give us the substitution instances we need; the first two are
the induction step and the basis.
This ALT version of nnind 11645 has a different hypothesis order. It may be easier to use with the Metamath program Proof Assistant, because "MM-PA> ASSIGN LAST" will be applied to the substitution instances first. We may eventually use this one as the official version. You may use either version. After the proof is complete, the ALT version can be changed to the non-ALT version with "MM-PA> MINIMIZE_WITH nnind / MAYGROW". (Contributed by NM, 7-Dec-2005.) (New usage is discouraged.) (Proof modification is discouraged.) |
⊢ (𝑦 ∈ ℕ → (𝜒 → 𝜃)) & ⊢ 𝜓 & ⊢ (𝑥 = 1 → (𝜑 ↔ 𝜓)) & ⊢ (𝑥 = 𝑦 → (𝜑 ↔ 𝜒)) & ⊢ (𝑥 = (𝑦 + 1) → (𝜑 ↔ 𝜃)) & ⊢ (𝑥 = 𝐴 → (𝜑 ↔ 𝜏)) ⇒ ⊢ (𝐴 ∈ ℕ → 𝜏) | ||
Theorem | nn1m1nn 11647 | Every positive integer is one or a successor. (Contributed by Mario Carneiro, 16-May-2014.) |
⊢ (𝐴 ∈ ℕ → (𝐴 = 1 ∨ (𝐴 − 1) ∈ ℕ)) | ||
Theorem | nn1suc 11648* | If a statement holds for 1 and also holds for a successor, it holds for all positive integers. The first three hypotheses give us the substitution instances we need; the last two show that it holds for 1 and for a successor. (Contributed by NM, 11-Oct-2004.) (Revised by Mario Carneiro, 16-May-2014.) |
⊢ (𝑥 = 1 → (𝜑 ↔ 𝜓)) & ⊢ (𝑥 = (𝑦 + 1) → (𝜑 ↔ 𝜒)) & ⊢ (𝑥 = 𝐴 → (𝜑 ↔ 𝜃)) & ⊢ 𝜓 & ⊢ (𝑦 ∈ ℕ → 𝜒) ⇒ ⊢ (𝐴 ∈ ℕ → 𝜃) | ||
Theorem | nnaddcl 11649 | Closure of addition of positive integers, proved by induction on the second addend. (Contributed by NM, 12-Jan-1997.) |
⊢ ((𝐴 ∈ ℕ ∧ 𝐵 ∈ ℕ) → (𝐴 + 𝐵) ∈ ℕ) | ||
Theorem | nnmulcl 11650 | Closure of multiplication of positive integers. (Contributed by NM, 12-Jan-1997.) Remove dependency on ax-mulcom 10590 and ax-mulass 10592. (Revised by Steven Nguyen, 24-Sep-2022.) |
⊢ ((𝐴 ∈ ℕ ∧ 𝐵 ∈ ℕ) → (𝐴 · 𝐵) ∈ ℕ) | ||
Theorem | nnmulcli 11651 | Closure of multiplication of positive integers. (Contributed by Mario Carneiro, 18-Feb-2014.) |
⊢ 𝐴 ∈ ℕ & ⊢ 𝐵 ∈ ℕ ⇒ ⊢ (𝐴 · 𝐵) ∈ ℕ | ||
Theorem | nnmtmip 11652 | "Minus times minus is plus, The reason for this we need not discuss." (W. H. Auden, as quoted in M. Guillen "Bridges to Infinity", p. 64, see also Metamath Book, section 1.1.1, p. 5) This statement, formalized to "The product of two negative integers is a positive integer", is proved by the following theorem, therefore it actually need not be discussed anymore. "The reason for this" is that (-𝐴 · -𝐵) = (𝐴 · 𝐵) for all complex numbers 𝐴 and 𝐵 because of mul2neg 11068, 𝐴 and 𝐵 are complex numbers because of nncn 11635, and (𝐴 · 𝐵) ∈ ℕ because of nnmulcl 11650. This also holds for positive reals, see rpmtmip 12403. Note that the opposites -𝐴 and -𝐵 of the positive integers 𝐴 and 𝐵 are negative integers. (Contributed by AV, 23-Dec-2022.) |
⊢ ((𝐴 ∈ ℕ ∧ 𝐵 ∈ ℕ) → (-𝐴 · -𝐵) ∈ ℕ) | ||
Theorem | nn2ge 11653* | There exists a positive integer greater than or equal to any two others. (Contributed by NM, 18-Aug-1999.) |
⊢ ((𝐴 ∈ ℕ ∧ 𝐵 ∈ ℕ) → ∃𝑥 ∈ ℕ (𝐴 ≤ 𝑥 ∧ 𝐵 ≤ 𝑥)) | ||
Theorem | nnge1 11654 | A positive integer is one or greater. (Contributed by NM, 25-Aug-1999.) |
⊢ (𝐴 ∈ ℕ → 1 ≤ 𝐴) | ||
Theorem | nngt1ne1 11655 | A positive integer is greater than one iff it is not equal to one. (Contributed by NM, 7-Oct-2004.) |
⊢ (𝐴 ∈ ℕ → (1 < 𝐴 ↔ 𝐴 ≠ 1)) | ||
Theorem | nnle1eq1 11656 | A positive integer is less than or equal to one iff it is equal to one. (Contributed by NM, 3-Apr-2005.) |
⊢ (𝐴 ∈ ℕ → (𝐴 ≤ 1 ↔ 𝐴 = 1)) | ||
Theorem | nngt0 11657 | A positive integer is positive. (Contributed by NM, 26-Sep-1999.) |
⊢ (𝐴 ∈ ℕ → 0 < 𝐴) | ||
Theorem | nnnlt1 11658 | A positive integer is not less than one. (Contributed by NM, 18-Jan-2004.) (Revised by Mario Carneiro, 27-May-2016.) |
⊢ (𝐴 ∈ ℕ → ¬ 𝐴 < 1) | ||
Theorem | nnnle0 11659 | A positive integer is not less than or equal to zero . (Contributed by AV, 13-May-2020.) |
⊢ (𝐴 ∈ ℕ → ¬ 𝐴 ≤ 0) | ||
Theorem | nnne0 11660 | A positive integer is nonzero. See nnne0ALT 11664 for a shorter proof using ax-pre-mulgt0 10603. This proof avoids 0lt1 11151, and thus ax-pre-mulgt0 10603, by splitting ax-1ne0 10595 into the two separate cases 0 < 1 and 1 < 0. (Contributed by NM, 27-Sep-1999.) Remove dependency on ax-pre-mulgt0 10603. (Revised by Steven Nguyen, 30-Jan-2023.) |
⊢ (𝐴 ∈ ℕ → 𝐴 ≠ 0) | ||
Theorem | nnneneg 11661 | No positive integer is equal to its negation. (Contributed by AV, 20-Jun-2023.) |
⊢ (𝐴 ∈ ℕ → 𝐴 ≠ -𝐴) | ||
Theorem | 0nnn 11662 | Zero is not a positive integer. (Contributed by NM, 25-Aug-1999.) Remove dependency on ax-pre-mulgt0 10603. (Revised by Steven Nguyen, 30-Jan-2023.) |
⊢ ¬ 0 ∈ ℕ | ||
Theorem | 0nnnALT 11663 | Alternate proof of 0nnn 11662, which requires ax-pre-mulgt0 10603 but is not based on nnne0 11660 (and which can therefore be used in nnne0ALT 11664). (Contributed by NM, 25-Aug-1999.) (New usage is discouraged.) (Proof modification is discouraged.) |
⊢ ¬ 0 ∈ ℕ | ||
Theorem | nnne0ALT 11664 | Alternate version of nnne0 11660. A positive integer is nonzero. (Contributed by NM, 27-Sep-1999.) (New usage is discouraged.) (Proof modification is discouraged.) |
⊢ (𝐴 ∈ ℕ → 𝐴 ≠ 0) | ||
Theorem | nngt0i 11665 | A positive integer is positive (inference version). (Contributed by NM, 17-Sep-1999.) |
⊢ 𝐴 ∈ ℕ ⇒ ⊢ 0 < 𝐴 | ||
Theorem | nnne0i 11666 | A positive integer is nonzero (inference version). (Contributed by NM, 25-Aug-1999.) |
⊢ 𝐴 ∈ ℕ ⇒ ⊢ 𝐴 ≠ 0 | ||
Theorem | nndivre 11667 | The quotient of a real and a positive integer is real. (Contributed by NM, 28-Nov-2008.) |
⊢ ((𝐴 ∈ ℝ ∧ 𝑁 ∈ ℕ) → (𝐴 / 𝑁) ∈ ℝ) | ||
Theorem | nnrecre 11668 | The reciprocal of a positive integer is real. (Contributed by NM, 8-Feb-2008.) |
⊢ (𝑁 ∈ ℕ → (1 / 𝑁) ∈ ℝ) | ||
Theorem | nnrecgt0 11669 | The reciprocal of a positive integer is positive. (Contributed by NM, 25-Aug-1999.) |
⊢ (𝐴 ∈ ℕ → 0 < (1 / 𝐴)) | ||
Theorem | nnsub 11670 | Subtraction of positive integers. (Contributed by NM, 20-Aug-2001.) (Revised by Mario Carneiro, 16-May-2014.) |
⊢ ((𝐴 ∈ ℕ ∧ 𝐵 ∈ ℕ) → (𝐴 < 𝐵 ↔ (𝐵 − 𝐴) ∈ ℕ)) | ||
Theorem | nnsubi 11671 | Subtraction of positive integers. (Contributed by NM, 19-Aug-2001.) |
⊢ 𝐴 ∈ ℕ & ⊢ 𝐵 ∈ ℕ ⇒ ⊢ (𝐴 < 𝐵 ↔ (𝐵 − 𝐴) ∈ ℕ) | ||
Theorem | nndiv 11672* | Two ways to express "𝐴 divides 𝐵 " for positive integers. (Contributed by NM, 3-Feb-2004.) (Proof shortened by Mario Carneiro, 16-May-2014.) |
⊢ ((𝐴 ∈ ℕ ∧ 𝐵 ∈ ℕ) → (∃𝑥 ∈ ℕ (𝐴 · 𝑥) = 𝐵 ↔ (𝐵 / 𝐴) ∈ ℕ)) | ||
Theorem | nndivtr 11673 | Transitive property of divisibility: if 𝐴 divides 𝐵 and 𝐵 divides 𝐶, then 𝐴 divides 𝐶. Typically, 𝐶 would be an integer, although the theorem holds for complex 𝐶. (Contributed by NM, 3-May-2005.) |
⊢ (((𝐴 ∈ ℕ ∧ 𝐵 ∈ ℕ ∧ 𝐶 ∈ ℂ) ∧ ((𝐵 / 𝐴) ∈ ℕ ∧ (𝐶 / 𝐵) ∈ ℕ)) → (𝐶 / 𝐴) ∈ ℕ) | ||
Theorem | nnge1d 11674 | A positive integer is one or greater. (Contributed by Mario Carneiro, 27-May-2016.) |
⊢ (𝜑 → 𝐴 ∈ ℕ) ⇒ ⊢ (𝜑 → 1 ≤ 𝐴) | ||
Theorem | nngt0d 11675 | A positive integer is positive. (Contributed by Mario Carneiro, 27-May-2016.) |
⊢ (𝜑 → 𝐴 ∈ ℕ) ⇒ ⊢ (𝜑 → 0 < 𝐴) | ||
Theorem | nnne0d 11676 | A positive integer is nonzero. (Contributed by Mario Carneiro, 27-May-2016.) |
⊢ (𝜑 → 𝐴 ∈ ℕ) ⇒ ⊢ (𝜑 → 𝐴 ≠ 0) | ||
Theorem | nnrecred 11677 | The reciprocal of a positive integer is real. (Contributed by Mario Carneiro, 27-May-2016.) |
⊢ (𝜑 → 𝐴 ∈ ℕ) ⇒ ⊢ (𝜑 → (1 / 𝐴) ∈ ℝ) | ||
Theorem | nnaddcld 11678 | Closure of addition of positive integers. (Contributed by Mario Carneiro, 27-May-2016.) |
⊢ (𝜑 → 𝐴 ∈ ℕ) & ⊢ (𝜑 → 𝐵 ∈ ℕ) ⇒ ⊢ (𝜑 → (𝐴 + 𝐵) ∈ ℕ) | ||
Theorem | nnmulcld 11679 | Closure of multiplication of positive integers. (Contributed by Mario Carneiro, 27-May-2016.) |
⊢ (𝜑 → 𝐴 ∈ ℕ) & ⊢ (𝜑 → 𝐵 ∈ ℕ) ⇒ ⊢ (𝜑 → (𝐴 · 𝐵) ∈ ℕ) | ||
Theorem | nndivred 11680 | A positive integer is one or greater. (Contributed by Mario Carneiro, 27-May-2016.) |
⊢ (𝜑 → 𝐴 ∈ ℝ) & ⊢ (𝜑 → 𝐵 ∈ ℕ) ⇒ ⊢ (𝜑 → (𝐴 / 𝐵) ∈ ℝ) | ||
The decimal representation of numbers/integers is based on the decimal digits 0 through 9 (df-0 10533 through df-9 11696), which are explicitly defined in the following. Note that the numbers 0 and 1 are constants defined as primitives of the complex number axiom system (see df-0 10533 and df-1 10534). With the decimal constructor df-dec 12088, it is possible to easily express larger integers in base 10. See deccl 12102 and the theorems that follow it. See also 4001prm 16468 (4001 is prime) and the proof of bpos 25797. Note that the decimal constructor builds on the definitions in this section. Note: The number 10 will be represented by its digits using the decimal constructor only, i.e., by ;10. Therefore, only decimal digits are needed (as symbols) for the decimal representation of a number. Integers can also be exhibited as sums of powers of 10 (e.g. the number 103 can be expressed as ((;10↑2) + 3)) or as some other expression built from operations on the numbers 0 through 9. For example, the prime number 823541 can be expressed as (7↑7) − 2. Decimals can be expressed as ratios of integers, as in cos2bnd 15531. Most abstract math rarely requires numbers larger than 4. Even in Wiles' proof of Fermat's Last Theorem, the largest number used appears to be 12. | ||
Syntax | c2 11681 | Extend class notation to include the number 2. |
class 2 | ||
Syntax | c3 11682 | Extend class notation to include the number 3. |
class 3 | ||
Syntax | c4 11683 | Extend class notation to include the number 4. |
class 4 | ||
Syntax | c5 11684 | Extend class notation to include the number 5. |
class 5 | ||
Syntax | c6 11685 | Extend class notation to include the number 6. |
class 6 | ||
Syntax | c7 11686 | Extend class notation to include the number 7. |
class 7 | ||
Syntax | c8 11687 | Extend class notation to include the number 8. |
class 8 | ||
Syntax | c9 11688 | Extend class notation to include the number 9. |
class 9 | ||
Definition | df-2 11689 | Define the number 2. (Contributed by NM, 27-May-1999.) |
⊢ 2 = (1 + 1) | ||
Definition | df-3 11690 | Define the number 3. (Contributed by NM, 27-May-1999.) |
⊢ 3 = (2 + 1) | ||
Definition | df-4 11691 | Define the number 4. (Contributed by NM, 27-May-1999.) |
⊢ 4 = (3 + 1) | ||
Definition | df-5 11692 | Define the number 5. (Contributed by NM, 27-May-1999.) |
⊢ 5 = (4 + 1) | ||
Definition | df-6 11693 | Define the number 6. (Contributed by NM, 27-May-1999.) |
⊢ 6 = (5 + 1) | ||
Definition | df-7 11694 | Define the number 7. (Contributed by NM, 27-May-1999.) |
⊢ 7 = (6 + 1) | ||
Definition | df-8 11695 | Define the number 8. (Contributed by NM, 27-May-1999.) |
⊢ 8 = (7 + 1) | ||
Definition | df-9 11696 | Define the number 9. (Contributed by NM, 27-May-1999.) |
⊢ 9 = (8 + 1) | ||
Theorem | 0ne1 11697 | Zero is different from one (the commuted form is the axiom ax-1ne0 10595). (Contributed by David A. Wheeler, 8-Dec-2018.) |
⊢ 0 ≠ 1 | ||
Theorem | 1m1e0 11698 | One minus one equals zero. (Contributed by David A. Wheeler, 7-Jul-2016.) |
⊢ (1 − 1) = 0 | ||
Theorem | 2nn 11699 | 2 is a positive integer. (Contributed by NM, 20-Aug-2001.) |
⊢ 2 ∈ ℕ | ||
Theorem | 2re 11700 | The number 2 is real. (Contributed by NM, 27-May-1999.) |
⊢ 2 ∈ ℝ |
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