The integral is infinite if you let phi go all the way to phim. If you restrict the upper limit of the integral to be less than phim you can get a finite result, but the value of the resulting integral will depend on the value you set for the upper limit.
Also, if you use a value of zero for y, you will get a divide by zero error, so you should probably start y at a small, but non-zero, value.
You can do the above numerically - you don't need symbolics.
