Project the given surface S on xy-plane.Then the projection on the xy-plane is the region R bounded by the circle Let
Therefore the given surface integral=
If the given surface S can be written as --(2),then the normal vector to S is
Let n denote the unit vector,then ,by using (2)
The required integral is using (2)
Now the integration can be evaluated as below.
=,other integral vanish because their integrands are odd function of x and y respectively.
=, on putting