The longest side of a right-angled triangle is the hypotenuse. The hypotenuse is always opposite the right angle. Draw a square ... This is Pythagoras' theorem. Pythagoras' theorem states that ...

Pythagoras’ theorem is a statement ... of the square on the hypotenuse close hypotenuseThe longest side of a right-angled triangle, which is always opposite the right angle.

What it means is that in a right triangle (where one angle equals 90°), the sum of the squares of two sides equals the square of the hypotenuse (the longest side).