# Proving the Pythagorean Theorem

## Some algebraic and geometric proofs of the best-known theorem of all time

A right triangle is a triangle in which one of the three angles is **90°**. The triangle shown below is **right-angled** because the angle ⦣*ACB* between sides *a* and *b* is 90°. The side opposite the right angle, *c*, is called the **hypotenuse**.