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- Thread starter DODGEVIPER13
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I uploaded 2 parts of the answer

No time to check it thoroughly now, but 2 cooents:

1. you're using

2. curl(grad f) = 0 always. The curl of the gradient of a function is always zero. (Not all functions have gradients).

3 your writing is hard for me to read but it looks like you wrote grad when you meant div.

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Sorry that was one long run on sentence. I meant to say will it be ok if I take off I,j, and k?

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Sorry that was one long run on sentence. I meant to say will it be ok if I take off I,j, and k?

No. The gradient of a function is a vector. Therefore you need the three unit vectors. Do't use

The curl can only be taken of a vector. There is no such thing as the curl of a scalar.

It's a mathematical identity that curl (grad f) = 0 for any f. It's very good to remember that identity.

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If wikipedia listed it I'm sure it was right. But they must have had the unit vectors too?

(Now I know how you did so well with the gradients, right?)

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Ugggg that is all Wikipedia lists I'm gonna go to my instructors web page and check there

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WannabeNewton

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Ugggg that is all Wikipedia lists I'm gonna go to my instructors web page and check there

Never mind, I screwed you up & forgot you're now doing divergences, not gradients.

Divergence of a vector is a scalar so you don't attach the unit vectors.

Sorry!

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actually I screwed up the problem never said anything about divergence! That being said I corrected what I did and have uploaded it hopefully its ok!!

Oh, OK. I think I mistook this for another of your threads whichI think did have div's in them.

I am too lazy to check all your math steps but for curl[grad(f)] the answer must be zero so I'm afraid something went awry there.

Why don't you run grad(f) thru wolfram alpha to make sure you got that part right.

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ok how do I use wolfram for gradients?

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ok how do I use wolfram for gradients?

Stand by, I'll give it a shot, haven't done that myself yet ...

EDIT: OK, punch in " gradient of sin(theta)*cos(phi)/r " in their top window.

They don't include the unit vectors. They give you the r, theta and phi components in that order, separated by commas, instead. Dumb, but better than screwing up solving it ourselves!

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ok uploaded something else I can could use some assistance with

Can't read that. What happened with grad f?

Back in 1 hr.

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(A) A=xyUx+y^2Uy-xzUz

(B) B=pz^2Up+psin^2(phi)Uphi+2pzsin^2(phi)Uz

(C) C=rUr+rcos^2(theta)Uphi

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The previous post was in reference to my uploaded answer that could not be read.

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(A) y+2y-x

(B) z^2+sin(2phi)+2psin^2(phi)

(C) 1

These are my answers

(B) z^2+sin(2phi)+2psin^2(phi)

(C) 1

These are my answers

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(A) y+2y-x

(B) z^2+sin(2phi)+2psin^2(phi)

(C) 1

These are my answers

Unfortunately, B and C are incorrect. They are tricky so work carefully. And check your results with wolfram.

For example, B=pz

so what is ∂B

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look at what I came up with for the gradient and improvise! Play around with it for a while. I pointed out that it gave the gradient in comma-separated chunks, omitting the unit vectors. Wolfram will have examples of how to enter a vector to get the divergence.

I would suggest using r instead of rho.

Answer my post 22.

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Bp/p

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Whoops I meant what is Bp/p was that in the formula

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Did you look carefully? When I ran grad V3 it gave it in cartesian but also in spherical.

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Whoops I meant what is Bp/p was that in the formula

sure was! ∂B

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