The formula for Pythagoras' Theorem is \( a^2 + b^2 = c^2 \).
It is used to find unknown sides of a right-angled triangle.
The longest side is called the hypotenuse and is labelled c.
A '3, 4, 5' triangle is a special kind of right-angled triangle where the side lengths are all whole numbers.
Another type is a '5, 12, 13' triangle.
Sometimes a question requires you to find a suitable right-angled triangle to use. You might have to split an isosceles triangle in half, for example.