P. 431 of Theorem List - Metamath Proof Explorer

Theorem List for Metamath Proof Explorer - 43001-43100   *Has distinct variable group(s)

Type	Label	Description
Statement
Theorem	indstrd 43001*	Strong induction, deduction version. (Contributed by Steven Nguyen, 13-Jul-2025.)
⊢ (𝑥 = 𝑦 → (𝜓 ↔ 𝜒))    &   ⊢ (𝑥 = 𝐴 → (𝜓 ↔ 𝜃))    &   ⊢ ((𝜑 ∧ 𝑥 ∈ ℕ ∧ ∀𝑦 ∈ ℕ (𝑦 < 𝑥 → 𝜒)) → 𝜓)    &   ⊢ (𝜑 → 𝐴 ∈ ℕ)    ⇒   ⊢ (𝜑 → 𝜃)
Theorem	grpods 43002*	Relate sums of elements of orders and roots of unity. (Contributed by metakunt, 14-Jul-2025.)
⊢ 𝐵 = (Base‘𝐺)    &   ⊢ ↑ = (.g‘𝐺)    &   ⊢ (𝜑 → 𝐺 ∈ Grp)    &   ⊢ (𝜑 → 𝐵 ∈ Fin)    &   ⊢ (𝜑 → 𝑁 ∈ ℕ)    ⇒   ⊢ (𝜑 → Σ𝑘 ∈ {𝑚 ∈ (1...𝑁) ∣ 𝑚 ∥ 𝑁} (♯‘{𝑥 ∈ 𝐵 ∣ ((od‘𝐺)‘𝑥) = 𝑘}) = (♯‘{𝑥 ∈ 𝐵 ∣ (𝑁 ↑ 𝑥) = (0g‘𝐺)}))
Theorem	unitscyglem1 43003*	Lemma for unitscyg . (Contributed by metakunt, 13-Jul-2025.)
⊢ 𝐵 = (Base‘𝐺)    &   ⊢ ↑ = (.g‘𝐺)    &   ⊢ (𝜑 → 𝐺 ∈ Grp)    &   ⊢ (𝜑 → 𝐵 ∈ Fin)    &   ⊢ (𝜑 → ∀𝑛 ∈ ℕ (♯‘{𝑥 ∈ 𝐵 ∣ (𝑛 ↑ 𝑥) = (0g‘𝐺)}) ≤ 𝑛)    &   ⊢ (𝜑 → 𝐴 ∈ 𝐵)    ⇒   ⊢ (𝜑 → (♯‘{𝑥 ∈ 𝐵 ∣ (((od‘𝐺)‘𝐴) ↑ 𝑥) = (0g‘𝐺)}) = ((od‘𝐺)‘𝐴))
Theorem	unitscyglem2 43004*	Lemma for unitscyg . (Contributed by metakunt, 13-Jul-2025.)
⊢ 𝐵 = (Base‘𝐺)    &   ⊢ ↑ = (.g‘𝐺)    &   ⊢ (𝜑 → 𝐺 ∈ Grp)    &   ⊢ (𝜑 → 𝐵 ∈ Fin)    &   ⊢ (𝜑 → ∀𝑛 ∈ ℕ (♯‘{𝑥 ∈ 𝐵 ∣ (𝑛 ↑ 𝑥) = (0g‘𝐺)}) ≤ 𝑛)    &   ⊢ (𝜑 → 𝐷 ∈ ℕ)    &   ⊢ (𝜑 → 𝐷 ∥ (♯‘𝐵))    &   ⊢ (𝜑 → 𝐴 ∈ 𝐵)    &   ⊢ (𝜑 → ((od‘𝐺)‘𝐴) = 𝐷)    &   ⊢ (𝜑 → ∀𝑐 ∈ ℕ (𝑐 < 𝐷 → ((𝑐 ∥ (♯‘𝐵) ∧ {𝑥 ∈ 𝐵 ∣ ((od‘𝐺)‘𝑥) = 𝑐} ≠ ∅) → (♯‘{𝑥 ∈ 𝐵 ∣ ((od‘𝐺)‘𝑥) = 𝑐}) = (ϕ‘𝑐))))    ⇒   ⊢ (𝜑 → (♯‘{𝑥 ∈ 𝐵 ∣ ((od‘𝐺)‘𝑥) = 𝐷}) = (ϕ‘𝐷))
Theorem	unitscyglem3 43005*	Lemma for unitscyg . (Contributed by metakunt, 14-Jul-2025.)
⊢ 𝐵 = (Base‘𝐺)    &   ⊢ ↑ = (.g‘𝐺)    &   ⊢ (𝜑 → 𝐺 ∈ Grp)    &   ⊢ (𝜑 → 𝐵 ∈ Fin)    &   ⊢ (𝜑 → ∀𝑛 ∈ ℕ (♯‘{𝑥 ∈ 𝐵 ∣ (𝑛 ↑ 𝑥) = (0g‘𝐺)}) ≤ 𝑛)    ⇒   ⊢ (𝜑 → ∀𝑑 ∈ ℕ ((𝑑 ∥ (♯‘𝐵) ∧ {𝑥 ∈ 𝐵 ∣ ((od‘𝐺)‘𝑥) = 𝑑} ≠ ∅) → (♯‘{𝑥 ∈ 𝐵 ∣ ((od‘𝐺)‘𝑥) = 𝑑}) = (ϕ‘𝑑)))
Theorem	unitscyglem4 43006*	Lemma for unitscyg . (Contributed by metakunt, 14-Jul-2025.)
⊢ 𝐵 = (Base‘𝐺)    &   ⊢ ↑ = (.g‘𝐺)    &   ⊢ (𝜑 → 𝐺 ∈ Grp)    &   ⊢ (𝜑 → 𝐵 ∈ Fin)    &   ⊢ (𝜑 → ∀𝑛 ∈ ℕ (♯‘{𝑥 ∈ 𝐵 ∣ (𝑛 ↑ 𝑥) = (0g‘𝐺)}) ≤ 𝑛)    &   ⊢ (𝜑 → 𝐷 ∈ ℕ)    &   ⊢ (𝜑 → 𝐷 ∥ (♯‘𝐵))    ⇒   ⊢ (𝜑 → (♯‘{𝑦 ∈ 𝐵 ∣ ((od‘𝐺)‘𝑦) = 𝐷}) = (ϕ‘𝐷))
Theorem	unitscyglem5 43007	Lemma for unitscyg . (Contributed by metakunt, 9-Aug-2025.)
⊢ 𝐺 = ((mulGrp‘𝑅) ↾s (Unit‘𝑅))    &   ⊢ (𝜑 → 𝑅 ∈ IDomn)    &   ⊢ (𝜑 → (Base‘𝑅) ∈ Fin)    &   ⊢ (𝜑 → 𝐷 ∈ ℕ)    &   ⊢ (𝜑 → 𝐷 ∥ (♯‘(Base‘𝐺)))    ⇒   ⊢ (𝜑 → ((mulGrp‘𝑅) PrimRoots 𝐷) ≠ ∅)
Theorem	aks5lem7 43008*	Lemma for aks5. We clean up the hypotheses compared to aks5lem6 43000. (Contributed by metakunt, 9-Aug-2025.)
⊢ (𝜑 → (♯‘(Base‘𝐾)) ∈ ℕ)    &   ⊢ 𝑃 = (chr‘𝐾)    &   ⊢ (𝜑 → 𝐾 ∈ Field)    &   ⊢ (𝜑 → 𝑃 ∈ ℙ)    &   ⊢ (𝜑 → 𝑅 ∈ ℕ)    &   ⊢ (𝜑 → 𝑁 ∈ (ℤ≥‘3))    &   ⊢ (𝜑 → 𝑃 ∥ 𝑁)    &   ⊢ (𝜑 → (𝑁 gcd 𝑅) = 1)    &   ⊢ 𝐴 = (⌊‘((√‘(ϕ‘𝑅)) · (2 logb 𝑁)))    &   ⊢ (𝜑 → ((2 logb 𝑁)↑2) < ((odℤ‘𝑅)‘𝑁))    &   ⊢ (𝜑 → 𝑅 ∥ ((♯‘(Base‘𝐾)) − 1))    &   ⊢ (𝜑 → ∀𝑎 ∈ (1...𝐴)[(𝑁(.g‘(mulGrp‘𝑆))(𝑋(+g‘𝑆)((ℤRHom‘𝑆)‘𝑎)))](𝑆 ~QG 𝐿) = [((𝑁(.g‘(mulGrp‘𝑆))𝑋)(+g‘𝑆)((ℤRHom‘𝑆)‘𝑎))](𝑆 ~QG 𝐿))    &   ⊢ (𝜑 → ∀𝑏 ∈ (1...𝐴)(𝑏 gcd 𝑁) = 1)    &   ⊢ 𝑆 = (Poly1‘(ℤ/nℤ‘𝑁))    &   ⊢ 𝐿 = ((RSpan‘𝑆)‘{((𝑅(.g‘(mulGrp‘𝑆))𝑋)(-g‘𝑆)(1r‘𝑆))})    &   ⊢ 𝑋 = (var1‘(ℤ/nℤ‘𝑁))    ⇒   ⊢ (𝜑 → 𝑁 = (𝑃↑(𝑃 pCnt 𝑁)))
Theorem	aks5lem8 43009*	Lemma for aks5. Clean up the conclusion. (Contributed by metakunt, 9-Aug-2025.)
⊢ (𝜑 → (♯‘(Base‘𝐾)) ∈ ℕ)    &   ⊢ 𝑃 = (chr‘𝐾)    &   ⊢ (𝜑 → 𝐾 ∈ Field)    &   ⊢ (𝜑 → 𝑃 ∈ ℙ)    &   ⊢ (𝜑 → 𝑅 ∈ ℕ)    &   ⊢ (𝜑 → 𝑁 ∈ (ℤ≥‘3))    &   ⊢ (𝜑 → 𝑃 ∥ 𝑁)    &   ⊢ (𝜑 → (𝑁 gcd 𝑅) = 1)    &   ⊢ 𝐴 = (⌊‘((√‘(ϕ‘𝑅)) · (2 logb 𝑁)))    &   ⊢ (𝜑 → ((2 logb 𝑁)↑2) < ((odℤ‘𝑅)‘𝑁))    &   ⊢ (𝜑 → 𝑅 ∥ ((♯‘(Base‘𝐾)) − 1))    &   ⊢ (𝜑 → ∀𝑎 ∈ (1...𝐴)[(𝑁(.g‘(mulGrp‘𝑆))(𝑋(+g‘𝑆)((ℤRHom‘𝑆)‘𝑎)))](𝑆 ~QG 𝐿) = [((𝑁(.g‘(mulGrp‘𝑆))𝑋)(+g‘𝑆)((ℤRHom‘𝑆)‘𝑎))](𝑆 ~QG 𝐿))    &   ⊢ (𝜑 → ∀𝑏 ∈ (1...𝐴)(𝑏 gcd 𝑁) = 1)    &   ⊢ 𝑆 = (Poly1‘(ℤ/nℤ‘𝑁))    &   ⊢ 𝐿 = ((RSpan‘𝑆)‘{((𝑅(.g‘(mulGrp‘𝑆))𝑋)(-g‘𝑆)(1r‘𝑆))})    &   ⊢ 𝑋 = (var1‘(ℤ/nℤ‘𝑁))    ⇒   ⊢ (𝜑 → ∃𝑝 ∈ ℙ ∃𝑛 ∈ ℕ 𝑁 = (𝑝↑𝑛))
Axiom	ax-exfinfld 43010*	Existence axiom for finite fields, eventually we want to construct them. (Contributed by metakunt, 13-Jul-2025.)
⊢ ∀𝑝 ∈ ℙ ∀𝑛 ∈ ℕ ∃𝑘 ∈ Field ((♯‘(Base‘𝑘)) = (𝑝↑𝑛) ∧ (chr‘𝑘) = 𝑝)
Theorem	exfinfldd 43011*	For any prime 𝑃 and any positive integer 𝑁 there exists a field 𝑘 such that 𝑘 contains 𝑃↑𝑁 elements. (Contributed by metakunt, 13-Jul-2025.)
⊢ (𝜑 → 𝑃 ∈ ℙ)    &   ⊢ (𝜑 → 𝑁 ∈ ℕ)    ⇒   ⊢ (𝜑 → ∃𝑘 ∈ Field ((♯‘(Base‘𝑘)) = (𝑃↑𝑁) ∧ (chr‘𝑘) = 𝑃))
Theorem	aks5 43012*	The AKS Primality test, given an integer 𝑁 greater than or equal to 3, find a coprime 𝑅 such that 𝑅 is big enough. Then, if a bunch of polynomial equalities in the residue ring hold then 𝑁 is a prime power. Currently depends on the axiom ax-exfinfld 43010, since we currently do not have the existence of finite fields in the database. (Contributed by metakunt, 16-Aug-2025.)
⊢ 𝐴 = (⌊‘((√‘(ϕ‘𝑅)) · (2 logb 𝑁)))    &   ⊢ 𝑋 = (var1‘(ℤ/nℤ‘𝑁))    &   ⊢ 𝑆 = (Poly1‘(ℤ/nℤ‘𝑁))    &   ⊢ 𝐿 = ((RSpan‘𝑆)‘{((𝑅(.g‘(mulGrp‘𝑆))𝑋)(-g‘𝑆)(1r‘𝑆))})    &   ⊢ (𝜑 → 𝑁 ∈ (ℤ≥‘3))    &   ⊢ (𝜑 → 𝑅 ∈ ℕ)    &   ⊢ (𝜑 → (𝑁 gcd 𝑅) = 1)    &   ⊢ (𝜑 → ((2 logb 𝑁)↑2) < ((odℤ‘𝑅)‘𝑁))    &   ⊢ (𝜑 → ∀𝑎 ∈ (1...𝐴)[(𝑁(.g‘(mulGrp‘𝑆))(𝑋(+g‘𝑆)((ℤRHom‘𝑆)‘𝑎)))](𝑆 ~QG 𝐿) = [((𝑁(.g‘(mulGrp‘𝑆))𝑋)(+g‘𝑆)((ℤRHom‘𝑆)‘𝑎))](𝑆 ~QG 𝐿))    &   ⊢ (𝜑 → ∀𝑎 ∈ (1...𝐴)(𝑎 gcd 𝑁) = 1)    ⇒   ⊢ (𝜑 → ∃𝑝 ∈ ℙ ∃𝑛 ∈ ℕ 𝑁 = (𝑝↑𝑛))
21.30  Mathbox for Luke Murphy
21.30.1  Solutions of quadratic equations
Theorem	quadfac 43013	The solution of a quadratic equation via factoring. (Contributed by Luke Murphy, 10-Jul-2026.)
⊢ (𝜑 → 𝐴 ∈ ℂ)    &   ⊢ (𝜑 → 𝐴 ≠ 0)    &   ⊢ (𝜑 → 𝐵 ∈ ℂ)    &   ⊢ (𝜑 → 𝐶 ∈ ℂ)    &   ⊢ (𝜑 → 𝑋 ∈ ℂ)    &   ⊢ (𝜑 → 𝑀 ∈ ℂ)    &   ⊢ (𝜑 → 𝑁 ∈ ℂ)    &   ⊢ (𝜑 → (𝑀 + 𝑁) = -(𝐵 / 𝐴))    &   ⊢ (𝜑 → (𝑀 · 𝑁) = (𝐶 / 𝐴))    ⇒   ⊢ (𝜑 → (((𝐴 · (𝑋↑2)) + ((𝐵 · 𝑋) + 𝐶)) = 0 ↔ (𝑋 = 𝑀 ∨ 𝑋 = 𝑁)))
21.30.2  April Fool's theorem
Theorem	25or6to4 43014	Question 67 of 68 from a lecture Prof. Loof Lirpa held last Saturday in Lincoln Park. When asked why the smaller root wasn't reduced to 3/2, Lirpa responded "It really doesn't matter anyhow." (Contributed by Luke Murphy, 10-Jul-2026.)
⊢ (𝜑 → 𝐴 = 1)    &   ⊢ (𝜑 → 𝐵 = -(;53 / 2))    &   ⊢ (𝜑 → 𝐶 = (;75 / 2))    &   ⊢ (𝜑 → 𝑋 ∈ ℂ)    ⇒   ⊢ (𝜑 → (((𝐴 · (𝑋↑2)) + ((𝐵 · 𝑋) + 𝐶)) = 0 ↔ (𝑋 = ;25 ∨ 𝑋 = (6 / 4))))
21.31  Mathbox for Steven Nguyen
21.31.1  Utility theorems
Theorem	jarrii 43015	Inference associated with jarri 108. A consequence of ax-mp 5 and ax-1 6. (Contributed by SN, 14-Oct-2025.)
⊢ 𝜓    &   ⊢ ((𝜑 → 𝜓) → 𝜒)    ⇒   ⊢ 𝜒
Theorem	intnanrt 43016	Introduction of conjunct inside of a contradiction. Would be used in elfvov1 7465. (Contributed by SN, 18-May-2025.)
⊢ (¬ 𝜑 → ¬ (𝜑 ∧ 𝜓))
Theorem	ioin9i8 43017	Miscellaneous inference creating a biconditional from an implied converse implication. (Contributed by Steven Nguyen, 17-Jul-2022.)
⊢ (𝜑 → (𝜓 ∨ 𝜒))    &   ⊢ (𝜒 → ¬ 𝜃)    &   ⊢ (𝜓 → 𝜃)    ⇒   ⊢ (𝜑 → (𝜓 ↔ 𝜃))
Theorem	jaodd 43018	Double deduction form of jaoi 871. (Contributed by Steven Nguyen, 17-Jul-2022.)
⊢ (𝜑 → (𝜓 → (𝜒 → 𝜃)))    &   ⊢ (𝜑 → (𝜓 → (𝜏 → 𝜃)))    ⇒   ⊢ (𝜑 → (𝜓 → ((𝜒 ∨ 𝜏) → 𝜃)))
Theorem	syl3an12 43019	A double syllogism inference. (Contributed by SN, 15-Sep-2024.)
⊢ (𝜑 → 𝜓)    &   ⊢ (𝜒 → 𝜃)    &   ⊢ ((𝜓 ∧ 𝜃 ∧ 𝜏) → 𝜂)    ⇒   ⊢ ((𝜑 ∧ 𝜒 ∧ 𝜏) → 𝜂)
Theorem	exbiii 43020	Inference associated with exbii 1881. Weaker version of eximii 1870. (Contributed by SN, 14-Oct-2025.)
⊢ ∃𝑥𝜑    &   ⊢ (𝜑 ↔ 𝜓)    ⇒   ⊢ ∃𝑥𝜓
Theorem	sbtd 43021*	A true statement is true upon substitution (deduction). A similar proof is possible for icht 48242. (Contributed by SN, 4-May-2024.)
⊢ (𝜑 → 𝜓)    ⇒   ⊢ (𝜑 → [𝑡 / 𝑥]𝜓)
Theorem	sbor2 43022	One direction of sbor 2344, using fewer axioms. Compare 19.33 1917. (Contributed by Steven Nguyen, 18-Aug-2023.)
⊢ (([𝑡 / 𝑥]𝜑 ∨ [𝑡 / 𝑥]𝜓) → [𝑡 / 𝑥](𝜑 ∨ 𝜓))
Theorem	sbalexi 43023*	Inference form of sbalex 2281, avoiding ax-10 2179 by using ax-gen 1828. (Contributed by SN, 12-Aug-2025.)
⊢ ∃𝑥(𝑥 = 𝑦 ∧ 𝜑)    ⇒   ⊢ ∀𝑥(𝑥 = 𝑦 → 𝜑)
Theorem	nfalh 43024	Version of nfal 2359 with an 'h' hypothesis, avoiding ax-12 2216. (Contributed by SN, 11-Feb-2026.)
⊢ (𝜑 → ∀𝑥𝜑)    ⇒   ⊢ Ⅎ𝑥∀𝑦𝜑
Theorem	nfe2 43025	An inner existential quantifier's variable is bound. (Contributed by SN, 11-Feb-2026.)
⊢ Ⅎ𝑥∃𝑦∃𝑥𝜑
Theorem	nfale2 43026	An inner existential quantifier's variable is bound. (Contributed by SN, 11-Feb-2026.)
⊢ Ⅎ𝑥∀𝑦∃𝑥𝜑
Theorem	19.9dev 43027*	19.9d 2242 in the case of an existential quantifier, avoiding the ax-10 2179 from nfex 2360 that would be used for the hypothesis of 19.9d 2242, at the cost of an additional DV condition on 𝑦, 𝜑. (Contributed by SN, 26-May-2024.)
⊢ (𝜑 → Ⅎ𝑥𝜓)    ⇒   ⊢ (𝜑 → (∃𝑥∃𝑦𝜓 ↔ ∃𝑦𝜓))
Theorem	3rspcedvd 43028*	Triple application of rspcedvd 3586. (Contributed by Steven Nguyen, 27-Feb-2023.)
⊢ (𝜑 → 𝐴 ∈ 𝐷)    &   ⊢ (𝜑 → 𝐵 ∈ 𝐷)    &   ⊢ (𝜑 → 𝐶 ∈ 𝐷)    &   ⊢ ((𝜑 ∧ 𝑥 = 𝐴) → (𝜓 ↔ 𝜒))    &   ⊢ ((𝜑 ∧ 𝑦 = 𝐵) → (𝜒 ↔ 𝜃))    &   ⊢ ((𝜑 ∧ 𝑧 = 𝐶) → (𝜃 ↔ 𝜏))    &   ⊢ (𝜑 → 𝜏)    ⇒   ⊢ (𝜑 → ∃𝑥 ∈ 𝐷 ∃𝑦 ∈ 𝐷 ∃𝑧 ∈ 𝐷 𝜓)
Theorem	sn-axrep5v 43029*	A condensed form of axrep5 5251. (Contributed by SN, 21-Sep-2023.)
⊢ (∀𝑤 ∈ 𝑥 ∃*𝑧𝜑 → ∃𝑦∀𝑧(𝑧 ∈ 𝑦 ↔ ∃𝑤 ∈ 𝑥 𝜑))
Theorem	sn-axprlem3 43030*	axprlem3 5401 using only Tarski's FOL axiom schemes and ax-rep 5243. (Contributed by SN, 22-Sep-2023.)
⊢ ∃𝑦∀𝑧(𝑧 ∈ 𝑦 ↔ ∃𝑤 ∈ 𝑥 if-(𝜑, 𝑧 = 𝑎, 𝑧 = 𝑏))
Theorem	sn-exelALT 43031*	Alternate proof of exel 5420, avoiding ax-pr 5409 but requiring ax-5 1943, ax-9 2156, and ax-pow 5341. This is similar to how elALT2 5345 uses ax-pow 5341 instead of ax-pr 5409 compared to el 5424. (Contributed by SN, 18-Sep-2023.) (Proof modification is discouraged.) (New usage is discouraged.)
⊢ ∃𝑦∃𝑥 𝑥 ∈ 𝑦
Theorem	ssabdv 43032*	Deduction of abstraction subclass from implication. (Contributed by SN, 22-Dec-2024.)
⊢ (𝜑 → (𝑥 ∈ 𝐴 → 𝜓))    ⇒   ⊢ (𝜑 → 𝐴 ⊆ {𝑥 ∣ 𝜓})
Theorem	sn-iotalem 43033*	An unused lemma showing that many equivalences involving df-iota 6499 are potentially provable without ax-10 2179, ax-11 2195, ax-12 2216. (Contributed by SN, 6-Nov-2024.)
⊢ {𝑦 ∣ {𝑥 ∣ 𝜑} = {𝑦}} = {𝑧 ∣ {𝑦 ∣ {𝑥 ∣ 𝜑} = {𝑦}} = {𝑧}}
Theorem	sn-iotalemcor 43034*	Corollary of sn-iotalem 43033. Compare sb8iota 6510. (Contributed by SN, 6-Nov-2024.)
⊢ (℩𝑥𝜑) = (℩𝑦{𝑥 ∣ 𝜑} = {𝑦})
Theorem	abbi1sn 43035*	Originally part of uniabio 6513. Convert a theorem about df-iota 6499 to one about dfiota2 6500, without ax-10 2179, ax-11 2195, ax-12 2216. Although, eu6 2605 uses ax-10 2179 and ax-12 2216. (Contributed by SN, 23-Nov-2024.)
⊢ (∀𝑥(𝜑 ↔ 𝑥 = 𝑦) → {𝑥 ∣ 𝜑} = {𝑦})
Theorem	brif2 43036	Move a relation inside and outside the conditional operator. (Contributed by SN, 14-Aug-2024.)
⊢ (𝐶𝑅if(𝜑, 𝐴, 𝐵) ↔ if-(𝜑, 𝐶𝑅𝐴, 𝐶𝑅𝐵))
Theorem	brif12 43037	Move a relation inside and outside the conditional operator. (Contributed by SN, 14-Aug-2024.)
⊢ (if(𝜑, 𝐴, 𝐵)𝑅if(𝜑, 𝐶, 𝐷) ↔ if-(𝜑, 𝐴𝑅𝐶, 𝐵𝑅𝐷))
Theorem	pssexg 43038	The proper subset of a set is also a set. (Contributed by Steven Nguyen, 17-Jul-2022.)
⊢ ((𝐴 ⊊ 𝐵 ∧ 𝐵 ∈ 𝐶) → 𝐴 ∈ V)
Theorem	pssn0 43039	A proper superset is nonempty. (Contributed by Steven Nguyen, 17-Jul-2022.)
⊢ (𝐴 ⊊ 𝐵 → 𝐵 ≠ ∅)
Theorem	psspwb 43040	Classes are proper subclasses if and only if their power classes are proper subclasses. (Contributed by Steven Nguyen, 17-Jul-2022.)
⊢ (𝐴 ⊊ 𝐵 ↔ 𝒫 𝐴 ⊊ 𝒫 𝐵)
Theorem	xppss12 43041	Proper subset theorem for Cartesian product. (Contributed by Steven Nguyen, 17-Jul-2022.)
⊢ ((𝐴 ⊊ 𝐵 ∧ 𝐶 ⊊ 𝐷) → (𝐴 × 𝐶) ⊊ (𝐵 × 𝐷))
Theorem	elpwbi 43042	Membership in a power set, biconditional. (Contributed by Steven Nguyen, 17-Jul-2022.) (Proof shortened by Steven Nguyen, 16-Sep-2022.)
⊢ 𝐵 ∈ V    ⇒   ⊢ (𝐴 ⊆ 𝐵 ↔ 𝐴 ∈ 𝒫 𝐵)
Theorem	imaopab 43043*	The image of a class of ordered pairs. (Contributed by Steven Nguyen, 6-Jun-2023.)
⊢ ({⟨𝑥, 𝑦⟩ ∣ 𝜑} “ 𝐴) = {𝑦 ∣ ∃𝑥 ∈ 𝐴 𝜑}
Theorem	eqresfnbd 43044	Property of being the restriction of a function. Note that this is closer to funssres 6587 than fnssres 6665. (Contributed by SN, 11-Mar-2025.)
⊢ (𝜑 → 𝐹 Fn 𝐵)    &   ⊢ (𝜑 → 𝐴 ⊆ 𝐵)    ⇒   ⊢ (𝜑 → (𝑅 = (𝐹 ↾ 𝐴) ↔ (𝑅 Fn 𝐴 ∧ 𝑅 ⊆ 𝐹)))
Theorem	fmpocos 43045*	Composition of two functions. Variation of fmpoco 8099 with more context in the substitution hypothesis for 𝑇. (Contributed by SN, 14-Mar-2025.)
⊢ ((𝜑 ∧ (𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵)) → 𝑅 ∈ 𝐶)    &   ⊢ (𝜑 → 𝐹 = (𝑥 ∈ 𝐴, 𝑦 ∈ 𝐵 ↦ 𝑅))    &   ⊢ (𝜑 → 𝐺 = (𝑧 ∈ 𝐶 ↦ 𝑆))    &   ⊢ ((𝜑 ∧ (𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵)) → ⦋𝑅 / 𝑧⦌𝑆 = 𝑇)    ⇒   ⊢ (𝜑 → (𝐺 ∘ 𝐹) = (𝑥 ∈ 𝐴, 𝑦 ∈ 𝐵 ↦ 𝑇))
Theorem	ovmpogad 43046*	Value of an operation given by a maps-to rule. Deduction form of ovmpoga 7577. (Contributed by SN, 14-Mar-2025.)
⊢ 𝐹 = (𝑥 ∈ 𝐶, 𝑦 ∈ 𝐷 ↦ 𝑅)    &   ⊢ ((𝑥 = 𝐴 ∧ 𝑦 = 𝐵) → 𝑅 = 𝑆)    &   ⊢ (𝜑 → 𝐴 ∈ 𝐶)    &   ⊢ (𝜑 → 𝐵 ∈ 𝐷)    &   ⊢ (𝜑 → 𝑆 ∈ 𝑉)    ⇒   ⊢ (𝜑 → (𝐴𝐹𝐵) = 𝑆)
Theorem	ofun 43047	A function operation of unions of disjoint functions is a union of function operations. (Contributed by SN, 16-Jun-2024.)
⊢ (𝜑 → 𝐴 Fn 𝑀)    &   ⊢ (𝜑 → 𝐵 Fn 𝑀)    &   ⊢ (𝜑 → 𝐶 Fn 𝑁)    &   ⊢ (𝜑 → 𝐷 Fn 𝑁)    &   ⊢ (𝜑 → 𝑀 ∈ 𝑉)    &   ⊢ (𝜑 → 𝑁 ∈ 𝑊)    &   ⊢ (𝜑 → (𝑀 ∩ 𝑁) = ∅)    ⇒   ⊢ (𝜑 → ((𝐴 ∪ 𝐶) ∘f 𝑅(𝐵 ∪ 𝐷)) = ((𝐴 ∘f 𝑅𝐵) ∪ (𝐶 ∘f 𝑅𝐷)))
Theorem	dfqs3 43048*	Alternate definition of quotient set. (Contributed by Steven Nguyen, 7-Jun-2023.)
⊢ (𝐴 / 𝑅) = ∪ 𝑥 ∈ 𝐴 {[𝑥]𝑅}
Theorem	qseq12d 43049	Equality theorem for quotient set, deduction form. (Contributed by Steven Nguyen, 30-Apr-2023.)
⊢ (𝜑 → 𝐴 = 𝐵)    &   ⊢ (𝜑 → 𝐶 = 𝐷)    ⇒   ⊢ (𝜑 → (𝐴 / 𝐶) = (𝐵 / 𝐷))
Theorem	qsalrel 43050*	The quotient set is equal to the singleton of 𝐴 when all elements are related and 𝐴 is nonempty. (Contributed by SN, 8-Jun-2023.)
⊢ ((𝜑 ∧ (𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐴)) → 𝑥 ∼ 𝑦)    &   ⊢ (𝜑 → ∼ Er 𝐴)    &   ⊢ (𝜑 → 𝑁 ∈ 𝐴)    ⇒   ⊢ (𝜑 → (𝐴 / ∼ ) = {𝐴})
Theorem	supinf 43051*	The supremum is the infimum of the upper bounds. (Contributed by SN, 29-Jun-2025.)
⊢ (𝜑 → < Or 𝐴)    &   ⊢ (𝜑 → ∃𝑥 ∈ 𝐴 (∀𝑦 ∈ 𝐵 ¬ 𝑥 < 𝑦 ∧ ∀𝑦 ∈ 𝐴 (𝑦 < 𝑥 → ∃𝑧 ∈ 𝐵 𝑦 < 𝑧)))    ⇒   ⊢ (𝜑 → sup(𝐵, 𝐴, < ) = inf({𝑥 ∈ 𝐴 ∣ ∀𝑤 ∈ 𝐵 ¬ 𝑥 < 𝑤}, 𝐴, < ))
Theorem	mapcod 43052	Compose two mappings. (Contributed by SN, 11-Mar-2025.)
⊢ (𝜑 → 𝐹 ∈ (𝐴 ↑m 𝐵))    &   ⊢ (𝜑 → 𝐺 ∈ (𝐵 ↑m 𝐶))    ⇒   ⊢ (𝜑 → (𝐹 ∘ 𝐺) ∈ (𝐴 ↑m 𝐶))
Theorem	fisdomnn 43053	A finite set is dominated by the set of natural numbers. (Contributed by SN, 6-Jul-2025.)
⊢ (𝐴 ∈ Fin → 𝐴 ≺ ℕ)
Theorem	ltex 43054	The less-than relation is a set. (Contributed by SN, 5-Jun-2025.)
⊢ < ∈ V
Theorem	leex 43055	The less-than-or-equal-to relation is a set. (Contributed by SN, 5-Jun-2025.)
⊢ ≤ ∈ V
Theorem	subex 43056	The subtraction operation is a set. (Contributed by SN, 5-Jun-2025.)
⊢ − ∈ V
Theorem	absex 43057	The absolute value function is a set. (Contributed by SN, 5-Jun-2025.)
⊢ abs ∈ V
Theorem	cjex 43058	The conjugate function is a set. (Contributed by SN, 5-Jun-2025.)
⊢ ∗ ∈ V
Theorem	fzosumm1 43059*	Separate out the last term in a finite sum. (Contributed by Steven Nguyen, 22-Aug-2023.)
⊢ (𝜑 → (𝑁 − 1) ∈ (ℤ≥‘𝑀))    &   ⊢ ((𝜑 ∧ 𝑘 ∈ (𝑀..^𝑁)) → 𝐴 ∈ ℂ)    &   ⊢ (𝑘 = (𝑁 − 1) → 𝐴 = 𝐵)    &   ⊢ (𝜑 → 𝑁 ∈ ℤ)    ⇒   ⊢ (𝜑 → Σ𝑘 ∈ (𝑀..^𝑁)𝐴 = (Σ𝑘 ∈ (𝑀..^(𝑁 − 1))𝐴 + 𝐵))
Theorem	ccatcan2d 43060	Cancellation law for concatenation. (Contributed by SN, 6-Sep-2023.)
⊢ (𝜑 → 𝐴 ∈ Word 𝑉)    &   ⊢ (𝜑 → 𝐵 ∈ Word 𝑉)    &   ⊢ (𝜑 → 𝐶 ∈ Word 𝑉)    ⇒   ⊢ (𝜑 → ((𝐴 ++ 𝐶) = (𝐵 ++ 𝐶) ↔ 𝐴 = 𝐵))
21.31.2  Arithmetic theorems Towards the start of this section are several proofs regarding the different complex number axioms that could be used to prove some results. For example, ax-1rid 11188 is used in mulrid 11224 related theorems, so one could trade off the extra axioms in mulrid 11224 for the axioms needed to prove that something is a real number. Another example is avoiding complex number closure laws by using real number closure laws and then using ax-resscn 11175; in the other direction, real number closure laws can be avoided by using ax-resscn 11175 and then the complex number closure laws. (This only works if the result of (𝐴 + 𝐵) only needs to be a complex number). The natural numbers are especially amenable to axiom reductions, as the set ℕ is the recursive set {1, (1 + 1), ((1 + 1) + 1)}, etc., i.e. the set of numbers formed by only additions of 1. The digits 2 through 9 are defined so that they expand into additions of 1. This conveniently allows for adding natural numbers by rearranging parentheses, as shown below: (4 + 3) = 7 ((3 + 1) + (2 + 1)) = (6 + 1) ((((1 + 1) + 1) + 1) + ((1 + 1) + 1)) = ((((((1 + 1) + 1) + 1) + 1) + 1) + 1) This only requires ax-addass 11183, ax-1cn 11176, and ax-addcl 11178. (And in practice, the expression isn't fully expanded into ones.) Multiplication by 1 requires either mullidi 11232 or (ax-1rid 11188 and 1re 11226) as seen in 1t1e1 12420 and 1t1e1ALT 12309. Multiplying with greater natural numbers uses ax-distr 11185. Still, this takes fewer axioms than adding zero, which is often implicit in theorems such as (9 + 1) = ;10. Adding zero uses almost every complex number axiom, though notably not ax-mulcom 11182 (see readdrid 43212 and readdlid 43205).
Theorem	c0exALT 43061	Alternate proof of c0ex 11218 using more set theory axioms but fewer complex number axioms (add ax-10 2179, ax-11 2195, ax-13 2407, ax-nul 5274, and remove ax-1cn 11176, ax-icn 11177, ax-addcl 11178, and ax-mulcl 11180). (Contributed by Steven Nguyen, 4-Dec-2022.) (Proof modification is discouraged.) (New usage is discouraged.)
⊢ 0 ∈ V
Theorem	0cnALT3 43062	Alternate proof of 0cn 11216 using ax-resscn 11175, ax-addrcl 11179, ax-rnegex 11189, ax-cnre 11191 instead of ax-icn 11177, ax-addcl 11178, ax-mulcl 11180, ax-i2m1 11186. Version of 0cnALT 11463 using ax-1cn 11176 instead of ax-icn 11177. (Contributed by Steven Nguyen, 7-Jan-2022.) (Proof modification is discouraged.) (New usage is discouraged.)
⊢ 0 ∈ ℂ
Theorem	elre0re 43063	Specialized version of 0red 11229 without using ax-1cn 11176 and ax-cnre 11191. (Contributed by Steven Nguyen, 28-Jan-2023.)
⊢ (𝐴 ∈ ℝ → 0 ∈ ℝ)
Theorem	lttrii 43064	'Less than' is transitive. (Contributed by SN, 26-Aug-2025.)
⊢ 𝐴 ∈ ℝ    &   ⊢ 𝐵 ∈ ℝ    &   ⊢ 𝐶 ∈ ℝ    &   ⊢ 𝐴 < 𝐵    &   ⊢ 𝐵 < 𝐶    ⇒   ⊢ 𝐴 < 𝐶
Theorem	remulcan2d 43065	mulcan2d 11866 for real numbers using fewer axioms. (Contributed by Steven Nguyen, 15-Apr-2023.)
⊢ (𝜑 → 𝐴 ∈ ℝ)    &   ⊢ (𝜑 → 𝐵 ∈ ℝ)    &   ⊢ (𝜑 → 𝐶 ∈ ℝ)    &   ⊢ (𝜑 → 𝐶 ≠ 0)    ⇒   ⊢ (𝜑 → ((𝐴 · 𝐶) = (𝐵 · 𝐶) ↔ 𝐴 = 𝐵))
Theorem	readdridaddlidd 43066	Given some real number 𝐵 where 𝐴 acts like a right additive identity, derive that 𝐴 is a left additive identity. Note that the hypothesis is weaker than proving that 𝐴 is a right additive identity (for all numbers). Although, if there is a right additive identity, then by readdcan 11402, 𝐴 is the right additive identity. (Contributed by Steven Nguyen, 14-Jan-2023.)
⊢ (𝜑 → 𝐴 ∈ ℝ)    &   ⊢ (𝜑 → 𝐵 ∈ ℝ)    &   ⊢ (𝜑 → (𝐵 + 𝐴) = 𝐵)    ⇒   ⊢ ((𝜑 ∧ 𝐶 ∈ ℝ) → (𝐴 + 𝐶) = 𝐶)
Theorem	1p3e4 43067	1 + 3 = 4. (Contributed by SN, 19-Nov-2025.)
⊢ (1 + 3) = 4
Theorem	5ne0 43068	The number 5 is nonzero. (Contributed by SN, 22-Oct-2025.)
⊢ 5 ≠ 0
Theorem	6ne0 43069	The number 6 is nonzero. (Contributed by SN, 22-Oct-2025.)
⊢ 6 ≠ 0
Theorem	7ne0 43070	The number 7 is nonzero. (Contributed by SN, 22-Oct-2025.)
⊢ 7 ≠ 0
Theorem	8ne0 43071	The number 8 is nonzero. (Contributed by SN, 22-Oct-2025.)
⊢ 8 ≠ 0
Theorem	9ne0 43072	The number 9 is nonzero. (Contributed by SN, 22-Oct-2025.)
⊢ 9 ≠ 0
Theorem	sn-1ne2 43073	A proof of 1ne2 12469 without using ax-mulcom 11182, ax-mulass 11184, ax-pre-mulgt0 11195. Based on mul02lem2 11405. (Contributed by SN, 13-Dec-2023.)
⊢ 1 ≠ 2
Theorem	nnn1suc 43074*	A positive integer that is not 1 is a successor of some other positive integer. (Contributed by Steven Nguyen, 19-Aug-2023.)
⊢ ((𝐴 ∈ ℕ ∧ 𝐴 ≠ 1) → ∃𝑥 ∈ ℕ (𝑥 + 1) = 𝐴)
Theorem	readdrcl2d 43075	Reverse closure for addition: the second addend is real if the first addend is real and the sum is real. (Contributed by SN, 25-Apr-2025.)
⊢ (𝜑 → 𝐴 ∈ ℝ)    &   ⊢ (𝜑 → 𝐵 ∈ ℂ)    &   ⊢ (𝜑 → (𝐴 + 𝐵) ∈ ℝ)    ⇒   ⊢ (𝜑 → 𝐵 ∈ ℝ)
Theorem	mvrrsubd 43076	Move a subtraction in the RHS to a right-addition in the LHS. Converse of mvlraddd 11642. EDITORIAL: Do not move until it would have 7 uses: current additional uses: (none). (Contributed by SN, 21-Aug-2024.)
⊢ (𝜑 → 𝐵 ∈ ℂ)    &   ⊢ (𝜑 → 𝐶 ∈ ℂ)    &   ⊢ (𝜑 → 𝐴 = (𝐵 − 𝐶))    ⇒   ⊢ (𝜑 → (𝐴 + 𝐶) = 𝐵)
Theorem	laddrotrd 43077	Rotate the variables right in an equation with addition on the left, converting it into a subtraction. Version of mvlladdd 11643 with a commuted consequent, and of mvrladdd 11645 with a commuted hypothesis. EDITORIAL: The label for this theorem is questionable. Do not move until it would have 7 uses: current additional uses: ply1dg3rt0irred 33905. (Contributed by SN, 21-Aug-2024.)
⊢ (𝜑 → 𝐴 ∈ ℂ)    &   ⊢ (𝜑 → 𝐵 ∈ ℂ)    &   ⊢ (𝜑 → (𝐴 + 𝐵) = 𝐶)    ⇒   ⊢ (𝜑 → (𝐶 − 𝐴) = 𝐵)
Theorem	raddswap12d 43078	Swap the first two variables in an equation with addition on the right, converting it into a subtraction. Version of mvrraddd 11644 with a commuted consequent, and of mvlraddd 11642 with a commuted hypothesis. EDITORIAL: The label for this theorem is questionable. Do not move until it would have 7 uses: current additional uses: (none). (Contributed by SN, 21-Aug-2024.)
⊢ (𝜑 → 𝐵 ∈ ℂ)    &   ⊢ (𝜑 → 𝐶 ∈ ℂ)    &   ⊢ (𝜑 → 𝐴 = (𝐵 + 𝐶))    ⇒   ⊢ (𝜑 → 𝐵 = (𝐴 − 𝐶))
Theorem	lsubrotld 43079	Rotate the variables left in an equation with subtraction on the left, converting it into an addition. EDITORIAL: The label for this theorem is questionable. Do not move until it would have 7 uses: current additional uses: (none). (Contributed by SN, 21-Aug-2024.)
⊢ (𝜑 → 𝐴 ∈ ℂ)    &   ⊢ (𝜑 → 𝐵 ∈ ℂ)    &   ⊢ (𝜑 → (𝐴 − 𝐵) = 𝐶)    ⇒   ⊢ (𝜑 → (𝐵 + 𝐶) = 𝐴)
Theorem	rsubrotld 43080	Rotate the variables left in an equation with subtraction on the right, converting it into an addition. EDITORIAL: The label for this theorem is questionable. Do not move until it would have 7 uses: current additional uses: (none). (Contributed by SN, 4-Jul-2025.)
⊢ (𝜑 → 𝐵 ∈ ℂ)    &   ⊢ (𝜑 → 𝐶 ∈ ℂ)    &   ⊢ (𝜑 → 𝐴 = (𝐵 − 𝐶))    ⇒   ⊢ (𝜑 → 𝐵 = (𝐶 + 𝐴))
Theorem	lsubswap23d 43081	Swap the second and third variables in an equation with subtraction on the left, converting it into an addition. EDITORIAL: The label for this theorem is questionable. Do not move until it would have 7 uses: current additional uses: (none). (Contributed by SN, 23-Aug-2024.)
⊢ (𝜑 → 𝐴 ∈ ℂ)    &   ⊢ (𝜑 → 𝐵 ∈ ℂ)    &   ⊢ (𝜑 → (𝐴 − 𝐵) = 𝐶)    ⇒   ⊢ (𝜑 → (𝐴 − 𝐶) = 𝐵)
Theorem	addsubeq4com 43082	Relation between sums and differences. (Contributed by Steven Nguyen, 5-Jan-2023.)
⊢ (((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ) ∧ (𝐶 ∈ ℂ ∧ 𝐷 ∈ ℂ)) → ((𝐴 + 𝐵) = (𝐶 + 𝐷) ↔ (𝐴 − 𝐶) = (𝐷 − 𝐵)))
Theorem	sqsumi 43083	A sum squared. (Contributed by Steven Nguyen, 16-Sep-2022.)
⊢ 𝐴 ∈ ℂ    &   ⊢ 𝐵 ∈ ℂ    ⇒   ⊢ ((𝐴 + 𝐵) · (𝐴 + 𝐵)) = (((𝐴 · 𝐴) + (𝐵 · 𝐵)) + (2 · (𝐴 · 𝐵)))
Theorem	negn0nposznnd 43084	Lemma for dffltz 43407. (Contributed by Steven Nguyen, 27-Feb-2023.)
⊢ (𝜑 → 𝐴 ≠ 0)    &   ⊢ (𝜑 → ¬ 0 < 𝐴)    &   ⊢ (𝜑 → 𝐴 ∈ ℤ)    ⇒   ⊢ (𝜑 → -𝐴 ∈ ℕ)
Theorem	sqmid3api 43085	Value of the square of the middle term of a 3-term arithmetic progression. (Contributed by Steven Nguyen, 20-Sep-2022.)
⊢ 𝐴 ∈ ℂ    &   ⊢ 𝑁 ∈ ℂ    &   ⊢ (𝐴 + 𝑁) = 𝐵    &   ⊢ (𝐵 + 𝑁) = 𝐶    ⇒   ⊢ (𝐵 · 𝐵) = ((𝐴 · 𝐶) + (𝑁 · 𝑁))
Theorem	decaddcom 43086	Commute ones place in addition. (Contributed by Steven Nguyen, 29-Jan-2023.)
⊢ 𝐴 ∈ ℕ0    &   ⊢ 𝐵 ∈ ℕ0    &   ⊢ 𝐶 ∈ ℕ0    ⇒   ⊢ (;𝐴𝐵 + 𝐶) = (;𝐴𝐶 + 𝐵)
Theorem	sqn5i 43087	The square of a number ending in 5. This shortcut only works because 5 is half of 10. (Contributed by Steven Nguyen, 16-Sep-2022.)
⊢ 𝐴 ∈ ℕ0    ⇒   ⊢ (;𝐴5 · ;𝐴5) = ;;(𝐴 · (𝐴 + 1))25
Theorem	sqn5ii 43088	The square of a number ending in 5. This shortcut only works because 5 is half of 10. (Contributed by Steven Nguyen, 16-Sep-2022.)
⊢ 𝐴 ∈ ℕ0    &   ⊢ (𝐴 + 1) = 𝐵    &   ⊢ (𝐴 · 𝐵) = 𝐶    ⇒   ⊢ (;𝐴5 · ;𝐴5) = ;;𝐶25
Theorem	decpmulnc 43089	Partial products algorithm for two digit multiplication, no carry. Compare muladdi 11683. (Contributed by Steven Nguyen, 9-Dec-2022.)
⊢ 𝐴 ∈ ℕ0    &   ⊢ 𝐵 ∈ ℕ0    &   ⊢ 𝐶 ∈ ℕ0    &   ⊢ 𝐷 ∈ ℕ0    &   ⊢ (𝐴 · 𝐶) = 𝐸    &   ⊢ ((𝐴 · 𝐷) + (𝐵 · 𝐶)) = 𝐹    &   ⊢ (𝐵 · 𝐷) = 𝐺    ⇒   ⊢ (;𝐴𝐵 · ;𝐶𝐷) = ;;𝐸𝐹𝐺
Theorem	decpmul 43090	Partial products algorithm for two digit multiplication. (Contributed by Steven Nguyen, 10-Dec-2022.)
⊢ 𝐴 ∈ ℕ0    &   ⊢ 𝐵 ∈ ℕ0    &   ⊢ 𝐶 ∈ ℕ0    &   ⊢ 𝐷 ∈ ℕ0    &   ⊢ (𝐴 · 𝐶) = 𝐸    &   ⊢ ((𝐴 · 𝐷) + (𝐵 · 𝐶)) = 𝐹    &   ⊢ (𝐵 · 𝐷) = ;𝐺𝐻    &   ⊢ (;𝐸𝐺 + 𝐹) = 𝐼    &   ⊢ 𝐺 ∈ ℕ0    &   ⊢ 𝐻 ∈ ℕ0    ⇒   ⊢ (;𝐴𝐵 · ;𝐶𝐷) = ;𝐼𝐻
Theorem	sqdeccom12 43091	The square of a number in terms of its digits switched. (Contributed by Steven Nguyen, 3-Jan-2023.)
⊢ 𝐴 ∈ ℕ0    &   ⊢ 𝐵 ∈ ℕ0    ⇒   ⊢ ((;𝐴𝐵 · ;𝐴𝐵) − (;𝐵𝐴 · ;𝐵𝐴)) = (;99 · ((𝐴 · 𝐴) − (𝐵 · 𝐵)))
Theorem	sq3deccom12 43092	Variant of sqdeccom12 43091 with a three digit square. (Contributed by Steven Nguyen, 3-Jan-2023.)
⊢ 𝐴 ∈ ℕ0    &   ⊢ 𝐵 ∈ ℕ0    &   ⊢ 𝐶 ∈ ℕ0    &   ⊢ (𝐴 + 𝐶) = 𝐷    ⇒   ⊢ ((;;𝐴𝐵𝐶 · ;;𝐴𝐵𝐶) − (;𝐷𝐵 · ;𝐷𝐵)) = (;99 · ((;𝐴𝐵 · ;𝐴𝐵) − (𝐶 · 𝐶)))
Theorem	4t5e20 43093	4 times 5 equals 20. (Contributed by SN, 30-Mar-2025.)
⊢ (4 · 5) = ;20
Theorem	3rdpwhole 43094	A third of a number plus the number is four thirds of the number. (Contributed by SN, 19-Nov-2025.)
⊢ (𝐴 ∈ ℂ → ((𝐴 / 3) + 𝐴) = (4 · (𝐴 / 3)))
Theorem	sq4 43095	The square of 4 is 16. (Contributed by SN, 26-Aug-2025.)
⊢ (4↑2) = ;16
Theorem	sq5 43096	The square of 5 is 25. (Contributed by SN, 26-Aug-2025.)
⊢ (5↑2) = ;25
Theorem	sq6 43097	The square of 6 is 36. (Contributed by SN, 26-Aug-2025.)
⊢ (6↑2) = ;36
Theorem	sq7 43098	The square of 7 is 49. (Contributed by SN, 26-Aug-2025.)
⊢ (7↑2) = ;49
Theorem	sq8 43099	The square of 8 is 64. (Contributed by SN, 26-Aug-2025.)
⊢ (8↑2) = ;64
Theorem	sq9 43100	The square of 9 is 81. (Contributed by SN, 30-Mar-2025.)
⊢ (9↑2) = ;81