# Math Help - Another directional derivative question

1. ## Another directional derivative question

The question
Find the directional derivative of:
f(x, y, z) = x arctan(y + z)
at P(1, 0, 1) in the direction of i + j − k

I got $\frac{\pi}{4\sqrt{3}}$

Is this correct? I don't have solutions.

Thanks.

2. Originally Posted by Glitch
The question
Find the directional derivative of:
f(x, y, z) = x arctan(y + z)
at P(1, 0, 1) in the direction of i + j − k

I got $\frac{\pi}{4\sqrt{3}}$

Is this correct? I don't have solutions.

Thanks.
Unrationalized, but correct.

-Dan