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## #1 2006-01-12 02:29:27

seiya_001
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### confusing trig problem...

can anybody tell me how to change

1     phi
-    ( ∫ A sin x . cos nx dx)
phi    0

into:

A     1     phi
-   .  -   . ∫(sin (1+n)x + sin (1-n)x )dx
phi    2    0

thanks before...

"If you can't have more age in your life, then have more life in your age..

## #2 2006-01-12 08:11:24

Ricky
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### Re: confusing trig problem...

To:

"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..."

## #3 2006-01-12 11:39:15

seiya_001
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### Re: confusing trig problem...

phi as in 180 deg... or is it pi

"If you can't have more age in your life, then have more life in your age..

## #4 2006-01-12 13:00:04

Ricky
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### Re: confusing trig problem...

That's pi.  Phi is normally the "vertical" (not sure exactly what to call it) angle when you are in spherical coordinates.

To:

First step, as always, is to simplify:

Now it becomes fairly simple, just use the trig identity:

Where a = x and b = nx

Which simplifies to:

Last edited by Ricky (2006-01-12 13:08:55)

"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..."

## #5 2006-01-12 14:19:53

seiya_001
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### Re: confusing trig problem...

thanks a lot bro
btw, do you have any reference where i can get a sumary of trig identity? thanks again...

"If you can't have more age in your life, then have more life in your age..

## #6 2006-01-12 15:02:58

Ricky
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### Re: confusing trig problem...

I have put it on my list to either create or find a website with even the most obscure trig identities.  So far, wikipedia (as always) is the best:

http://en.wikipedia.org/wiki/Trig_identities

"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..."

## #7 2006-01-12 19:24:43

seiya_001
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### Re: confusing trig problem...

thank you for the information...
god bless..

"If you can't have more age in your life, then have more life in your age..