# Thread: Partial derivative-need yr urgent help.

1. ## Partial derivative-need yr urgent help.

partial/partial z = tan^(-1) (z/x) .

Thank you very much.

2. Originally Posted by kittycat
partial/partial z = tan^(-1) (z/x) .

Thank you very much.
recall that $\frac d{dx} \arctan u = \frac {u'}{1 + u^2}$ where u is a function of x

we are taking the derivative with respect to z, so we treat x as if it was a constant.

Let $f(x,y,z) = \tan^{-1} \left( \frac zx \right)$

$\Rightarrow \frac {\partial f}{\partial z} = \frac 1{1 + \left( \frac zx \right)^2} \cdot \frac 1x$

and simplify