Finding directional deriviative

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SUMMARY

The discussion focuses on calculating the directional derivative of the function f(x,y) = (x*e^y) - (y*e^x) at the point P(0,0) in the direction of the vector a = 5i - 2j. The initial attempt resulted in a directional derivative of 0, which was incorrect. The correct approach involves calculating the gradient of f, which is not zero at (0,0), and then using the unit vector derived from the direction vector a to compute the directional derivative accurately.

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Homework Statement


Find the directional derivative of f at P in the direction of a
f(x,y)=(x*e^y)-(y*e^x); P(0,0);a=5i-2j

my answer came out to 0


The Attempt at a Solution



i got the unit vector from p to a, which came out to <5/√(29),-2/√(29))
and also the partial derivatives
i then took the gradient of f and got <0,0>
and then the directional derivative which came out to 0, is this right?
 
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"Directional vector from p to a" is meaningless. a is not a point- it is already the vector giving the direction. Just divide it by its length to get a unit vector.

The gradient vector, at (0, 0), is NOT 0. Do it again. What do you get for the gradient before you set x= 0, y= 0?
 

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