# Thread: partial derivative

1. ## partial derivative

Can someone pls tell me what the x partial derivative of:

(25-(x^2)-(y^2))^(1/2) is and how you would go about working it out.

2. ## all ok

it's ok - i worked it out.

3. Are you sure? If you want we can check your answer if you post it

4. Originally Posted by jedoob
Can someone pls tell me what the x partial derivative of:

(25-(x^2)-(y^2))^(1/2) is and how you would go about working it out.
Let me just post the answer so you can check with mine.
$z=\sqrt{25-x^2-y^2}$ consider $y$ a constant because you need to find $\frac{\partial z}{\partial x}$.
Thus, by the chain rule,
$\frac{1}{2}\cdot (-2x)(25-x^2-y^2)^{-1/2}$
Thus,
$-\frac{x}{\sqrt{25-(x^2+y^2)}}$