Pythagoras’ Theorem

$$a^2 + b^2 = c^2$$

If a triangle has sides $a$, $b$, and $c$ such that $$a^2 + b^2 = c^2$$, then the triangle is a right triangle.

In a right-angled triangle, the square of the length of the hypotenuse ($c$) is equal to the sum of the squares of the lengths of the other two sides ($a$ and $b$).