i had to try this out so i did it using a piece of paper (bad scissors, ruff edges)... i was loosing my mind and freaking out how is this possible. then i saw your comment and it was s slap back to sanity. THANK YOU!
The **** , I swear a couple of days ago everyone on FJ used to jack off to underage girls being attention whores, now everyone want to punch them in the face.
did everyone hit puberty .... AT THE SAME SYNCHRONIZED TIME?
On the upper triangle, the hypotenuse is curved inwards, and on the lower one it curves outwards. This extra area accounts for the remaining square (as the gif shows above). It's difficult to see because as humans, we just automatically assume it's straight.
I tried it at home, and in the second position, if you correctly realign the line sof the grid to make it a correct grid again, you'll see there's a gap where the diagonal cut is, that's where the surface area comes from.
if you put them togheter without the gap, the lines do not align.