The whole numbers a, b, and c are a Pythagorean triple if a and b are the lengths of two sides of a right triangle with hypotenuse c, so a2 + b2 = c2.

The same rule applies to right triangles, the shape you get when you slice a rectangle in half along its diagonal. The rule now sounds more like the one you learned in school: a2 + b2 = c2.

The triangle is coloured purple., This triangle will be used to show Pythagoras’ theorem that 𝒂² + 𝒃² = 𝒄². The hypotenuse of the right-angled triangle is labelled as 𝒄.