Similar to 角の二等分線の定理

Conic solid

Desargues's theorem

Heron's formula

Pompeiu's theorem

Regiomontanus' angle maximization problem

Exterior angle theorem

Midpoint theorem (triangle)

Droz-Farny line theorem

Napoleon's theorem

Feuerbach hyperbola

Maxwell's theorem (geometry)

Jacobi's theorem (geometry)

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Proof that 22/7 exceeds π

Proof that π is irrational

Euler's formula

Interesting number paradox

Open mapping theorem (complex analysis)