## Pythagoras' theorem

The **Pythagoras' theorem** (or *Pythagorean theorem*) states that:

"In a right-angled triangle, the square of the hypotenuse is equal to the sum of the squares of the other two sides."

So, if $a$, $b$, and $c$ are the three sides of a right-angled triangle and $c$ is the longest side (i.e. hypotenuse), then: $a^2 + b^2 = c^2$

The hypotenuse is the longest side of the right triangle and it always exists opposite to the right angle (90° angle) of the triangle. This happens because the side opposite to the greatest angle is the longest.