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.

STEP 1 - RIGHT TRIANGLE x 4: Take one piece of card and fold it in half, then fold it in half again... Image caption, ... use the ruler and pencil to draw a straight line across the bottom corner of ...