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## #1 2008-03-10 23:18:02

EMPhillips1989
Member
Registered: 2008-01-21
Posts: 40

### Calculus

let

i've found the gradient of f as

i now need to find the unit normal to the surface

at the point (2,-2,2)

Last edited by EMPhillips1989 (2008-03-11 00:39:22)

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## #2 2008-03-10 23:57:32

luca-deltodesco
Member
Registered: 2006-05-05
Posts: 1,470

### Re: Calculus

the gradient normalised IS the normal, substitute the values of x,y,z into the gradient function, and normalise the vector.

also, you should have -2xk not +2xk

Last edited by luca-deltodesco (2008-03-10 23:58:14)

The Beginning Of All Things To End.
The End Of All Things To Come.

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## #3 2008-03-11 00:36:02

EMPhillips1989
Member
Registered: 2008-01-21
Posts: 40

### Re: Calculus

So is this correct?

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## #4 2008-03-11 02:04:29

luca-deltodesco
Member
Registered: 2006-05-05
Posts: 1,470

### Re: Calculus

yeh, thats fine, but then you have to normalise it for the unit normal

so:

The Beginning Of All Things To End.
The End Of All Things To Come.

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## #5 2008-03-11 05:48:27

Ricky
Moderator
Registered: 2005-12-04
Posts: 3,791

### Re: Calculus

If my memory serves me right, this is the proper symbol for gradient:

"In the real world, this would be a problem.  But in mathematics, we can just define a place where this problem doesn't exist.  So we'll go ahead and do that now..."

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## #6 2017-03-16 18:41:34

Monox D. I-Fly
Member
Registered: 2015-12-02
Posts: 727

### Re: Calculus

Ricky wrote:

If my memory serves me right, this is the proper symbol for gradient:

I... never knew that despite I am a math graduate and often spend my time in math forums. In my country, gradient is generally symbolized as m.

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## #7 2017-03-16 22:12:58

zetafunc
Member
Registered: 2014-05-21
Posts: 1,823
Website

### Re: Calculus

Ricky wrote:

If my memory serves me right, this is the proper symbol for gradient:

Indeed, though
is my preference.
typically denotes the Laplace operator.

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