HELP: directional derivative problem....

Hello,

I am confused in as how to do this question.... any help, pointers etc. would be great.

http://img87.imageshack.us/img87/637/picture4nd7.png

Thanks

sarah :D

Its been a while since uni and whilst cross product and magnitude are fresh in my memory if you remind me of the definition of well lets call it the triangle I may be able to help

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Originally Posted by Glaysher

Its been a while since uni and whilst cross product and magnitude are fresh in my memory if you remind me of the definition of well lets call it the triangle I may be able to help

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'nabla' i think it is called, or the directional derivative as well i think....

http://img222.imageshack.us/img222/7406/picture1ji6.png

Shouldn't the definition be i(partial)d/dx + j(partial)d/dy + k(partial)d/dz

Let v = ai + bj + ck

Then v x r = (bz - cy)i + (cx - az)j + (ay - bx)k
|v x r| = sqrt[(bz - cy)² + (cx - az)² + (ay - bx)²]

Square out the brackets and collect like terms then do partial differentiation in terms of x and y and z to fulfill the definition for part (a)

Would have to dig out my notes for (b) and (c) but I'm afraid I've got an asleep baby son on me so won't be able to

yeah your right, that is the definition :)

would you please be able to help me quickly with part (b) of the question later on?

http://img134.imageshack.us/img134/4533/picture4zg4.png

Quote:

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Originally Posted by sarahisme

http://www.vbforums.com/

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I have arrived exactly at the same answer. :thumb:

wicked, thanks for that! :)