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Math Help - Find cos(a-b)

  1. #1
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    Find cos(a-b)

    Given that

    sin(a)+cos(b)= (3^(1/2))/2 and

    sin(a)+sin(b)=3/2

    Find cos(a-b).

    Can anyone help me?
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  2. #2
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    Re: Find cos(a-b)

    You should know that \displaystyle \cos{(\alpha \pm \beta)} \equiv \cos{(\alpha)}\cos{(\beta)} \mp \sin{(\alpha)}\sin{(\beta)}.

    What can you do with this?
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  3. #3
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    Re: Find cos(a-b)

    It may also be good to remember that \cos^{2}(x) + \sin^{2}(x) = 1
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  4. #4
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    Re: Find cos(a-b)

    The answer i get is 0.786... but the answer given is 0.5. What answer do you guys get?
    Last edited by MichaelLight; June 18th 2011 at 06:39 PM.
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  5. #5
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    Re: Find cos(a-b)

    How did you arrive at that? Please describe your process and let's check it out.
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