Pythagoras’ Theorem states that, in a right-angled triangle, the square of the longest side is equal to the sum of the squares of the other two sides.

Substitute the known lengths into Pythagoras’ theorem 17 2 = x 2 + 8 2 Calculate the value of the square of the missing side x 2 = 17 2 + 8 2 = 225 Find the square root of this value to get the length ...