Can anyone explain this? The Triangle riddle

[muse99]

OK, I'm sure you clever guys can sort this for me. I'm sure you've all seen this. I can't understand it at all and it's driving me nuts!! Help!

They both look the same and I have even measured them! It can be found here:

http://www.amazed.tv/video/13205-amazing-riddle-can-you-solve-it-how-is-this-possible.html

[Chi Meson]

The assumption is that it is a perfect triangle. Check out the slopes of the green and red mini triangles. Shouldn't they be the same? Are they? IF they were then the ratio of height to base would be the same. Does 2 over 5 equal 3 over 8?

[Smurf]

I think this was already posted somewhere, in the brain teaser forum?

[rcgldr]

Initially the upper surface of the not quite a triangle is "concave" (inwards angle), and after re-arrangment, the upper surface of the not quite a triangle is "convex" (outwards angle). The difference in area "consumed" by the "concave" uppper surface and the "convex" upper surface equals the area of the square.