# simplify and proof that answer is this

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• Dec 9th 2012, 05:45 AM
MarkFL
Re: simplify and proof that answer is this
What do you have so far for the first one?
• Dec 9th 2012, 06:43 AM
tautvyduks
Re: simplify and proof that answer is this
i dont know what to do with 1/2 sin (alpha) how to simplify it with
• Dec 9th 2012, 07:32 AM
topsquark
Re: simplify and proof that answer is this
I previously posted:

Quote:

Originally Posted by topsquark
$\displaystyle sin(A - B) = sin(A)~cos(B) - sin(B)~cos(A)$

so we have:
$\displaystyle sin \left ( \frac{\pi}{3} - \alpha \right ) = sin \left ( \frac{\pi}{3} \right ) ~cos( \alpha ) - sin( \alpha) ~cos \left ( \frac{\pi}{3} \right )$

Fill in the sines and cosines of this line. Finish this line and you'll know what to do with the extra term.

Basically what I'm asking you to do is the following:
$\displaystyle sin \left ( \frac{\pi}{3} \right )$

and
$\displaystyle cos \left ( \frac{\pi}{3} \right )$

-Dan
• Dec 9th 2012, 12:18 PM
chris541125
Re: simplify and proof that answer is this
What is the answer to problem 1? Is it 0.8660Cosa?
• Dec 9th 2012, 01:26 PM
topsquark
Re: simplify and proof that answer is this
You need to simplify
$\displaystyle sin \left ( \frac{\pi}{3} - \alpha \right ) - \frac{1}{2} sin( \alpha )$

I gave you a way to expand out the $\displaystyle sin \left ( \frac{\pi}{3} - \alpha \right )$

When you do so you will see what to do with the sin(a) term.

I think your biggest problem is that you are using a calculator. Put it away. If you work with exact answers you will easily see what to do.

So again I ask you: What are
$\displaystyle sin \left ( \frac{\pi}{3} \right )$

and
$\displaystyle cos \left ( \frac{\pi}{3} \right )$

-Dan
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