http://www.flickr.com/photos/goaghantis/5488852921/
Answer: This comes under "optical illusion" 1. Calculate the wedge angle of the green wedge (tangent inverse of 2/5)= 21.8 degrees 2. Calculate the wedge angle of the red wedge (tangent inverse of 3/8)= 20.5 degrees. 3. When the composite wedge is stacked as shown in top figure the hypotenuse is somewhat "concave". The exact angle is 178.7 degrees 4. When the composite wedge is stacked as shown in the bottom figure the hypotenuse is somewhat convex. The exact angle is 181.3 degrees. 4. The difference between these two setups(concave and convex hypotenuse) creates an area equal to one square. Hope this helps. There is no magic just illusions.
