confusing trig problem...

seiya_001 · 2006-01-11 03:29:27

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...

Ricky · 2006-01-11 09:11:24

Is your question:

To:

seiya_001 · 2006-01-11 12:39:15

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

Ricky · 2006-01-11 14:00:04

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)

seiya_001 · 2006-01-11 15:19:53

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

Ricky · 2006-01-11 16:02:58

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

seiya_001 · 2006-01-11 20:24:43

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

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