Hi all, this is my first post here, i need some help proving this identity

(sinAsin2A +sin3Asin6A)/(sinAcis2A+sin3Acos6A) =tan5A

Thanks

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- July 1st 2009, 07:38 PMarzeProving an identity
Hi all, this is my first post here, i need some help proving this identity

(sinAsin2A +sin3Asin6A)/(sinAcis2A+sin3Acos6A) =tan5A

Thanks - July 1st 2009, 09:31 PMred_dog
Use these formulas:

And the right hand member must be - July 1st 2009, 09:56 PMyeongil
You'll have to use the product-to-sum formulas:

AND

So,

Then, use the sum-to-product formulas:

AND

Hmm, I'm getting**-tan 5A**...

01

EDIT: posted too late. red dog also got -tan 5A. - July 2nd 2009, 09:08 PMarze
In my book it DOES say that tan5A so i guess it would be a printing error because there is at least one other problem where the "-" sign is missing.

but thanks anyway!