I'm new at working with directional derivatives. I'm stuck on this problem. Would someone mind helping me with the "Point" and "Direction" parts of the problem. I'm just looking for a place to start, not for someone to do the problem for me. Thanks.
In each of the following, find the directional derivative of f at P in the given direction.
1. f(x,y)=xy(1-x^2-y^2), P=any point on the unit circle, Direction: in the direction of OP.
I found that the gradient of f is: <y(1-x^2-y^2)-2yx^2, x(1-x^2-y^2)-2xy^2>, so I'm stuck on finding P and the direction.