Lay three pairs of shoes on the floor in a right triangle. Measure each side. Check if a² + b² = c².
Try it
Sides 30 cm, 40 cm. Hypotenuse?
30² + 40² = 900 + 1600 = 2500. √2500 = 50 cm. So the hypotenuse should measure 50 cm.
There are over 350 known proofs of Pythagoras' theorem — including one by US President James Garfield.