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#1 2006-01-11 03:29:27

seiya_001
Member
Registered: 2005-08-23
Posts: 19

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... smile


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#2 2006-01-11 09:11:24

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

Re: confusing trig problem...

Is your question:

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..."

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#3 2006-01-11 12:39:15

seiya_001
Member
Registered: 2005-08-23
Posts: 19

Re: confusing trig problem...

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


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#4 2006-01-11 14:00:04

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

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 (2006-01-11 14:08:55)


"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..."

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#5 2006-01-11 15:19:53

seiya_001
Member
Registered: 2005-08-23
Posts: 19

Re: confusing trig problem...

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


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

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#6 2006-01-11 16:02:58

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

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..."

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#7 2006-01-11 20:24:43

seiya_001
Member
Registered: 2005-08-23
Posts: 19

Re: confusing trig problem...

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


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

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