The first and second diagrams are similar, just using the 'outside' vs 'inside' deconstruction. If we label the sides a=3, b=4, and c=5 : The first diagram sh

The first and second diagrams are similar, just using the 'outside' vs 'inside' deconstruction. If we label the sides a=3, b=4, and c=5 : The first diagram shows that the big outer square of length (a+b) equals the area of the 4 triangles plus the rotated square of side c. (a+b)^2 = 2ab + c^2 [I'm not sure why they drew an inner 3x3 square on its own]. The second diagram puts the same four triangles inside the rotated square of side c, which leaves an extra smaller square of side (b-a) inside. c^2 = 2ab + (b-a)^2