What is the length of a hypotenuse?

A hypotenuse is the longest side of a right angled triangle. The length of a hypotenuse can be found using the Pythagorean Theorem. This states that in a right angled triangle, the square of the length of the hypotenuse is equal to the sum of the squares of the other two sides. This means that to find the length of the hypotenuse, you need to know the lengths of the other two sides.