  # Use Pythagoras' Theorem

In this worksheet, students will find the length of one of the shorter sides of a right-angled triangle using Pythagoras' Theorem. Key stage:  KS 3

Curriculum topic:   Geometry and Measures

Curriculum subtopic:   Solve Right-Angled Triangle Problems

Popular topics:   Geometry worksheets

Difficulty level:   #### Worksheet Overview

Pythagoras' Theorem states that:

In any right-angled triangle, the square of the hypotenuse is equal to the sum of the squares of the other two sides.

In the right-angled triangle below  a2 + b2 = c2 Remember that the triangle must be right-angled and that the hypotenuse is always the longest side and the one opposite the right angle.

Example

Use Pythagoras' Theorem to calculate the length of the side, a, in the following right-angled triangle.  Give your answer to 3 significant figures. By Pythagoras' Theorem:

a2 + 52 = 92

a2 + 25 = 81

a2 = 81 - 25 =56

a = √56

c = 7.48 (to 3 s.f.)

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