Pythagoras' Theorem can be used to calculate the length of the third side of a right angled triangle when given the lengths of the other two sides.
Before doing this section you should revise the National 4 Lifeskills Maths section on Pythagoras.
In a right-angled triangle there is a relationship among the three sides. This relationship is shown below.
In National 5 Lifeskills Maths it is likely that you will have to use Pythagoras' Theorem as one step in a bigger question.