Use
Theorem 13.9 to find the directional derivative of the function
at P in the direction of Q.

Data from in Theorem 13.9

Transcribed Image Text:

THEOREM 13.9 Directional Derivative If f is a differentiable function of x and y, then the directional derivative of fin the direction of the unit vector u = cos i + sin 0j is Duf(x, y) = f(x, y) cos 0 + f(x, y) sin 0.