In this triangle \(a^2 = b^2 + c^2\) and angle \(A\) is a right angle. Pythagoras' theorem only works for right-angled triangles, so you can use it to test whether a triangle has a right angle or not.

What it means is that in a right triangle (where one angle equals 90°), the sum of the squares of two sides equals the square of the hypotenuse (the longest side).

Pythagoras’ theorem is a statement that is ... hypotenuseThe longest side of a right-angled triangle, which is always opposite the right angle. When labelling a length as the hypotenuse, it ...