I've tried to derivate this function a couple of times but since I'm not very into all the rules I'm afraid I did it incorrect.

Will anyone tell me if this is right:

f(x)= (1/3)(pi)((xR/2pi)^2)((R^2)-((xR/2pi)^2))^0.5)

f'(x)= 1/3 * pi * (xR/2pi)^2

= (1/3)(pi)(2)(xR/2pi)(1/2pi)

= (1/3)(xR/2pi)

= xR/6pi

I'm sorry if it looks messy!

Thanks,