# Glossary (Version 8.4)

Pythagoras’ theorem states that for a right-angled triangle:

The square of the hypotenuse of a right-angled triangle equals the sum of the squares of the lengths of the other two sides.

In symbols, $$c^2=a^2+b^2$$.

The converse

If $$c^2=a^2+b^2$$ in a triangle ABC, then ∠C is a right angle.