f'(z) = du(x,y)/dx + i dv(x,y)/dx with z=x+iy

Hi,

What happens when I change for z=r*(cos(theta) + i*sin(theta))?

I get:

f'(z) = du(r*cos(theta),r*sin(theta))/dx + i dv(r*cos(theta),r*sin(theta))/dx

I can't derivate about dx anymore, as I don't have the variable x, it has been replaced by x=r*cos(theta) and y=r*sin(theta)... What happens to the derivative?

Btw, how to use the MATH tags??? I looked in the wiki and FAQ but found nothing...

Thanks!