# Thread: simplify and proof that answer is this

1. ## Re: simplify and proof that answer is this

What do you have so far for the first one?

2. ## Re: simplify and proof that answer is this

i dont know what to do with 1/2 sin (alpha) how to simplify it with

3. ## Re: simplify and proof that answer is this

I previously posted:

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

4. ## Re: simplify and proof that answer is this

What is the answer to problem 1? Is it 0.8660Cosa?

5. ## 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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