Similar to 正接定理

Dirichlet integral

Thébault's theorem

De Moivre's formula

Ptolemy's theorem

Sz.-Nagy's dilation theorem

Seven circles theorem

Napkin ring problem

Lazy caterer's sequence

Newton's theorem (quadrilateral)

Proof that e is irrational

Hardy–Littlewood inequality

Pappus's hexagon theorem

Banach–Alaoglu theorem

Banach fixed-point theorem

Tangent half-angle substitution

Pythagorean theorem

Lune of Hippocrates

Nyquist–Shannon sampling theorem

Fáry's theorem

Fatou's lemma

Feuerbach's theorem

Bézout's identity

Petr–Douglas–Neumann theorem

Helly's theorem

Poincaré–Bendixson theorem

Power of a point

Monge's theorem

Jacobi's formula