find the area of the triangles and smal ler square and add them together ; and find the area of the complete square and set them equal to each other (these are known truths)
triangle: l×w /2
square: s^2
There are 4 triangles so
4 (1/2ab)+c^2= (a+b)(a+b)
simplify
2ab+c^2= a^2+2ab+b^2
-2ab both sides
c^2=a^2+b^2
tada!! it's proven :)