Similar to 対角化定理

Five lemma

Gauss's lemma (number theory)

Kőnig's lemma

Fatou's lemma

Bézout's identity

Arzelà–Ascoli theorem

Apollonius point

Apollonius's theorem

Proof that 22/7 exceeds π

Proof that π is irrational

Euler's formula

Interesting number paradox

Open mapping theorem (complex analysis)

Rank–nullity theorem

Angle bisector theorem

Carathéodory's theorem (convex hull)

Leibniz formula for determinants

Locally connected space

Coupon collector's problem

Casey's theorem

Tree of primitive Pythagorean triples

Cauchy's mean value theorem

Mean value theorem (divided differences)

Shannon's source coding theorem

Noisy-channel coding theorem

Jordan's lemma

Stewart's theorem

Law of sines