Hi guys,

how do you prove these 2:

http://img29.imageshack.us/img29/5765/scan0001ik.jpg

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- Nov 28th 2009, 10:22 PMgp3Proving Trigo Identity
Hi guys,

how do you prove these 2:

http://img29.imageshack.us/img29/5765/scan0001ik.jpg - Nov 28th 2009, 10:37 PMalexmahone
- Nov 28th 2009, 10:53 PMGrandad
- Nov 28th 2009, 11:21 PMgp3
hi guys, thanks for your help.

I dont understand how you got this part: =\frac{\sin(3x+x)}{\tfrac12\sin2x}

and this part: =\frac{1}{\sqrt2}\left(\cos\frac{\theta}{2}-\sin\frac{\theta}{2}\right - Nov 28th 2009, 11:39 PMGrandad
- Nov 29th 2009, 12:24 AMgp3
http://www.mathhelpforum.com/math-he...ccb5afa9-1.gif

erm, i don't understand why is the part in bracket squared?

=\sqrt{\frac{1}{2}\left(1-\sin\theta\right)}

and how did you get to 1-Sin?

sorry for so many questions, i'm rather weak in my maths! - Nov 29th 2009, 12:58 AMGrandad