Pythagoras’s theorem

Pythagoras’s Theorem is related to right-angled triangles.

Here the sides of the triangle are labelled a, b and h.

The side labelled h is opposite the right-angle.

It is also the longest side.

The h stands for hypotenuse.

The hypotenuse is the longest side of a right-angled triangle.

I don’t know why the word hypotenuse was used for the longest side. The word comes from hypo- meaning under and a word meaning to stretch. To stretch under. You can think of the hypotenuse as the side stretched under the right-angle.

Pythagoras’s Theorem is that, for a right-angled triangle, the length of the hypothenuse squared is equal to the  sum of the squares of the lengths of the other two sides.

To write this as a mathematical formula we get:

h² = a² + b²