# Thread: Find Exact Value of SinB

1. ## Re: Find Exact Value of SinB

Originally Posted by JohnTerry
Thanks again, but how $\cos{\beta} = (-1)\cos{\alpha} + (0)\sin{\alpha} = -\cos{\alpha}$
= $\cos{\beta} = \cos{\pi}\cos{\alpha} + \sin{\pi}\sin{\alpha}$
$\pi$ is on the unit circle so there are exact values for $\sin(\pi)$ and $\cos(\pi)$. What level of trig are you at if you don't mind me asking? The unit circle is pretty elementary in trig.

What does (-1) and (0) mean?
Don't read too much into it: they're numbers.

2. ## Re: Find Exact Value of SinB

Originally Posted by JohnTerry
Thanks again, but how $\cos{\beta} = (-1)\cos{\alpha} + (0)\sin{\alpha} = -\cos{\alpha}$
= $\cos{\beta} = \cos{\pi}\cos{\alpha} + \sin{\pi}\sin{\alpha}$

What does (-1) and (0) mean?
$\cos{\pi} = -1$

$\sin{\pi} = 0$

you should know these from your unit circle values ...

3. ## Re: Find Exact Value of SinB

Originally Posted by JohnTerry
Thanks again, but how $\cos{\beta} = (-1)\cos{\alpha} + (0)\sin{\alpha} = -\cos{\alpha}$
= $\cos{\beta} = \cos{\pi}\cos{\alpha} + \sin{\pi}\sin{\alpha}$

What does (-1) and (0) mean?
Sorry, but it's time you made an effort and started thinking. Go back, review the thread, read the link, consider your class notes. There's been enough spoon-feeding for the time being.

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