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Math Help - [SOLVED] Double angle problem 2 (quick squaring question)

  1. #1
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    [SOLVED] Double angle problem 2 (quick squaring question)

    it says to solve for cos pi/3 using a double angle identity.
    I dont understand whats wrong.
    I do
    cos(pi/3)
    cos(2(pi/6)) <br />
= cos^2(pi/6)times sin^2(pi/6) This is where im stuck, what do you do when you have a squared sin/ cos, I know sin of pi/6 = 1/2 and cos = root 3 over 2 so dont you just square those so
    3/4 times 1/4?
    that gives the wrong answer though its supposed to be 1/2

    thanks.
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  2. #2
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    Quote Originally Posted by brentwoodbc View Post
    it says to solve for cos pi/3 using a double angle identity.
    I dont understand whats wrong.
    I do
    cos(pi/3)
    cos(2(pi/6)) \textcolor{red}{<br />
= cos^2(pi/6)times sin^2(pi/6)} This is where im stuck, what do you do when you have a squared sin/ cos, I know sin of pi/6 = 1/2 and cos = root 3 over 2 so dont you just square those so
    3/4 times 1/4?
    that gives the wrong answer though its supposed to be 1/2

    thanks.
    correction ...

    \cos^2\left(\frac{\pi}{6}\right) - \sin^2\left(\frac{\pi}{6}\right)
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  3. #3
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    thanks.
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