Also note that there are 4 curved portions of the belt and each of them are 1/4 of the circumference of a disc....
I'm not sure that I get what you mean, sorry.
Could you try and explain it again, please? I think I get the bit about the corners being a 1/4 of the circumference of a circle.
When you say sketch the square, do you mean mark the center of each circle and join up?
EDIT: I get it now. Thank you very much! It's very appreciated!