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**sousou****Member**- Registered: 2010-04-29
- Posts: 5

Hello,

I need your help to expand the following:

A = sqrt [C^2 + L^2 - 2*C*L cos (theta + phi)]

Where: C = sqrt[L^2 + (X + Y)^2]

phi = atan[(X+Y)/L]

L is a constant.

Thanks for your help and time.

*Last edited by sousou (2010-04-29 23:35:59)*

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**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606

Hi sousou;

This is the best I can do after 3 tries :

A little simpler:

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**** Always satisfy the Prime Directive of getting the right answer above all else.**

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**sousou****Member**- Registered: 2010-04-29
- Posts: 5

bobbym wrote:

Hi sousou;

This is the best I can do after 3 tries :

A little simpler:

Thanks Bobby,

could you please show the detailed workout o fthe three tries ...Thanks...

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**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606

Hi sousou;

There isn't anything to show just the 2 substitutions and a small cleanup. I didn't do very much here.

Make your substitutions:

Pull out a factor of 2L inside the radical:

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**** Always satisfy the Prime Directive of getting the right answer above all else.**

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**sousou****Member**- Registered: 2010-04-29
- Posts: 5

bobbym wrote:

Hi sousou;

There isn't anything to show just the 2 substitutions and a small cleanup. I didn't do very much here.

Make your substitutions:

Pull out a factor of 2L inside the radical:

Thanks lobby,

but all what you did is substitution

I am looking for further simplification, I wanna get rid of the square root :

A = sqrt [C^2 + L^2 - 2*C*L cos (theta + phi)] = A = [C^2 + L^2 - 2*C*L cos (theta + phi)]^1/2///

and then expand the polynomial...

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**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606

Hi sousou;

That is not a polynomial. How do you plan to expand it:

You could expand it as a Taylor series but that is all , I think.

I haven't worked on simplifying the terms underneath the radical. What I have in post # 4 might be all that is possible.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**** Always satisfy the Prime Directive of getting the right answer above all else.**

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**JaneFairfax****Member**- Registered: 2007-02-23
- Posts: 6,868

Hence

*Last edited by JaneFairfax (2010-04-30 03:16:53)*

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**sousou****Member**- Registered: 2010-04-29
- Posts: 5

Thanks ....I wonder how you could write the symbols of maths? is it the same sythax as lateX?

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**Monox D. I-Fly****Member**- Registered: 2015-12-02
- Posts: 926

sousou wrote:

Thanks ....I wonder how you could write the symbols of maths? is it the same sythax as lateX?

Yes.

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