Triple Integral of z over [0, 2*pi] for r [1, 2]

[kasse]

[SOLVED] Triple integral

Homework Statement

Calculate the triple integral of z when z [(r-1), sqrt(1-(r-2)^2)], r [1, 2], tetha [0, 2*pi]

2. The attempt at a solution

I've tried again and again, and I always get (17/4)*pi, while the answer is pi/2. Is there anything wrong with antiderivating in this order: dz, dr, d(tetha)?

 

[Defennder]

Is this problem solved yet or do you still need help?