Pythagoras’ Theorem for GCSE Maths: Explanation, Examples and Questions

Pythagoras’ Theorem is a key topic in GCSE maths, providing a method to find missing side lengths in right-angled triangles.

At GCSE level, you’ll learn how to use the formula a² + b² = c² to calculate the hypotenuse or the shorter sides of a right-angled triangle. The theorem is widely used in geometry, trigonometry, and practical applications such as construction and navigation.

A basic introduction to Pythagoras in 3D is also covered, with a link to a dedicated page for further learning.

GCSE Pythagoras’ Theorem

This video explains everything you need to know about Pythagoras’ Theorem, starting from the question 'What is Pythagoras’ Theorem?'.

Pythagoras in 3D

Pythagoras' theorem can also be applied to find the missing sides in 3D objects such as cuboids, other prisms, and pyramids.

To learn more about this go to our page on 3D Pythagoras.

The rest of the lesson on Pythagoras' theorem is not quite ready, but if you already know what you're doing, we have practice questions linked below.