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## Homework Statement

Let f(x,y,z)=sin(xy+z) and P=(0,-1, pi), Calculate Duf(P) where u is a unit vector making an angle 30°

=θ with dFp?

## Homework Equations

This is a two variable problem, where partials are necessary in order to find the gradient formula to get <dFP>. To take the Directional Derivative, from what I know, you require the following equation... <dFP>dot<U>/||u||.

## The Attempt at a Solution

from the following I calculated the gradient equation to be

<ycos(xy+z),xcos(xy+z),cos(xy+z)>

with the given gradient equation, I get dFP as <1,0,-1>.

What I cannot figure out is how to get the coordinates for the U vector.