Ill give this a crack:
assuming that the fact we are dealing with cubes and spheres makes no difference:
Need the difference between the length of the diagonal with 2 sides 10 and the diameter of the circle, then halved because there are two sections:
1/2*(10*SQRT3), then subtract the diameter of the cictle, which is 1/2*10.
then 5(sqrt3-1) is the answer
josh, what I don't get is sqrt(3)
if the edge is 10, then 5^2 + 5^2=50 so hyp. of triangle = 5sqrt(2)
how do I get 5sqrt(3)?