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Directional derivative

by teng125
Tags: derivative, directional
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teng125
#1
Jul17-06, 01:43 PM
P: 416
Find the directional derivative of f (x, y) = 5−x2−2y2 at P (-1, -1).
anybody pls help as i don't know how to find the direction from this ques so , i can't find the directional derivative


pls help
thanx
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neutrino
#2
Jul17-06, 02:02 PM
P: 2,046
Your question seems to be incomplete; please provide the complete question as it is given in the book. The directional derivative is the rate at which a function changes at some point in a particular direction.
Office_Shredder
#3
Jul17-06, 02:26 PM
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PF Gold
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Quote Quote by neutrino
The directional derivative is the rate at which a function changes at some point in a particular direction.
anybody pls help as i don't know how to find the direction from this ques so
I think that's what he's trying to figure out.

If you have absolutely no clue what direction it's in, I would guess that it's in the direction of the vector from the origin to P. Not for any particular reason, but because it's a better guess than anything else

Astronuc
#4
Jul17-06, 02:49 PM
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Directional derivative

http://mathworld.wolfram.com/DirectionalDerivative.html

Does the problem call for the directional derivative of the tangent, normal, or perhaps the directional derivative greatest magnitude?
HallsofIvy
#5
Jul17-06, 03:46 PM
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Thanks
PF Gold
P: 39,682
One more time: the problem as stated makes no sense. teng125, please state the entire problem as given in your textbook.


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