Right-angled triangles are useful for Pythagoras’ theorem.
The longest side of the triangle is called the hypotenuse, which is always opposite the right angle.
The longest side is called the hypotenuse and it is always opposite the right angle. In this example it is marked ‘a’.
The square of the length opposite to the hypotenuse is equal to the sum of the square of the other lengths.
Pythagoras’ theorem can only work for right-angled triangles.
(now find the square root of )
If you want to find the length of another side, you can rearrange the formula.