Hello,

Today, my teacher said that you have to use triple integrals to find the volume of sphere, minus a cylinder inside (x^{2}+ y = 1, x^{2}+ y^{2}+ z^{2}= 2), and you can't simply subtract the volumes because it doesn't take into account the "edge points." I understand how to do that in and of itself, but why can't you use subtraction of the volume of the individual figures? What does "edge points" mean?

Thanks.