See the picture below



Can you tell me the answer?

It's an optical illusion.The hypotenuse of both triangles seem to be straight lines but they're not.
I think the answer lies in the fact that neither shape is actually a triangle, they are quadrilaterals. They have four sides.

The side that looks like it is the hypotenuse is actually two sides, the corner being where the green and red triangle.
I have searched the web and find an answer here.

If you have any good explanation about this please let me know.