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Thread: Find Exact Value of SinB

  1. #16
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    e^(i*pi)'s Avatar
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    Re: Find Exact Value of SinB

    Quote Originally Posted by JohnTerry View Post
    Thanks again, but how $\displaystyle \cos{\beta} = (-1)\cos{\alpha} + (0)\sin{\alpha} = -\cos{\alpha}$
    = $\displaystyle \cos{\beta} = \cos{\pi}\cos{\alpha} + \sin{\pi}\sin{\alpha}$
    $\displaystyle \pi$ is on the unit circle so there are exact values for $\displaystyle \sin(\pi)$ and $\displaystyle \cos(\pi)$. 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.
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  2. #17
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    Re: Find Exact Value of SinB

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


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

    $\displaystyle \sin{\pi} = 0$

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

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  3. #18
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    Re: Find Exact Value of SinB

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


    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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