Welcome to this deck on Pythagoras' Theorem. This is a fundamental rule in geometry that connects the three sides of a very special type of triangle: the right-angled triangle. By the end of this deck, you'll be able to identify the key parts of a right-angled triangle and use the theorem to find the length of any missing side.

First, let's be clear what we're talking about. A right-angled triangle is any triangle that has one angle of exactly 90 degrees, often shown as a small square in the corner. The two sides that meet at the right angle are the shorter sides. The third side, which is always the longest and is opposite the right angle, has a special name: the hypotenuse.

The theorem itself is an equation. It states that for any right-angled triangle, if you call the two shorter sides 'a' and 'b', and you call the hypotenuse 'c', then 'a squared plus b squared equals c squared'. This relationship is always true for every right-angled triangle in existence.