Hey guy I'm having a problem with directional derivative, can any one give me a clue about how to solve this
at (-1,2) in the direction parallel to a vector clockwise from the positive x-axis
The directional derivative of function f in direction is the dot product of with the unit vector in direction . In two dimensional Cartesian coordinates, and the unit vector in the direction is so that dot product is just
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Surely you have seen that before?