Broken Triangle Explained

Surely they aren't the same?


Most people think this is a trick, and that the shapes aren't actually the same in each image. Not so!

The illusion lies in the fact that the red and green triangles appear to be similar. They are not. The green one is 1 square taller than the red. To be similar, it would need to be 7·5 squares long - it's actually 8! This leads to a shallower gradient on its sloping side:

Finally, overlaying the images, we can see where the "missing" square comes from. Clever, isn't it?!

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