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Math Help - [SOLVED] Trig Identities (short problem)

  1. #1
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    [SOLVED] Trig Identities (short problem)

    Hey guys, I need to find sin(3  \pi /8)
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    Rhymes with Orange Chris L T521's Avatar
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    Quote Originally Posted by goliath View Post
    Hey guys, I need to find sin(3  \pi /8)
    Note that \sin\!\left(\tfrac{3\pi}{8}\right)=\sin\!\left(\tf  rac{1}{2}\left(\tfrac{3\pi}{4}\right)\right).

    Now apply the half angle formula for sine with \theta=\frac{3\pi}{4}.

    Can you take it from here?
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  3. #3
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    Quote Originally Posted by goliath View Post
    Hey guys, I need to find sin(3  \pi /8)
    Alternatively, remember that \sin{\left(\frac{\pi}{2} - \theta\right)} = \cos{\theta}.

    Can you see that \frac{\pi}{2} - \frac{\pi}{8} = \frac{3\pi}{8}?


    So that would mean \sin{\frac{3\pi}{8}} = \cos{\frac{\pi}{8}}.

    And you've been told what that is...
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