
#1
Jul1706, 01:43 PM

P: 426

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 



#2
Jul1706, 02:02 PM

P: 2,048

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.




#3
Jul1706, 02:26 PM

Mentor
P: 4,499

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 



#4
Jul1706, 02:49 PM

Admin
P: 21,625

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? 



#5
Jul1706, 03:46 PM

Math
Emeritus
Sci Advisor
Thanks
PF Gold
P: 38,879

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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