(November 22, 2018 at 11:35 am)Grandizer Wrote: I was being serious, FTR.
Like Tibs said, the triangles are exactly the same and rearranged in the same way. That could only result in a square, not just any rhombus.
Polymath's answer is more rigorous, fair enough.
Something is required since the result fails for non-Euclidean geometry. And, in fact the point that fails is the angles are not right angles. The lines around the (a+b) squares are no longer straight.
