12 first of all, you have to understand that the circumscribed circle is actually a cube, so the radius of the circumscribed circle is half that of AC 1! According to Pythagorean theorem twice, we can get AC 1=3, so the volume of the circumscribed circle V=4/3π? r & ampsup2=36π

20(2), that's because the answer is wrong, and the one above is a square, not a square!