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Math Help - Usin sum, difference, and double-angle identities

  1. #1
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    Usin sum, difference, and double-angle identities

    Express cos(pi/6)cos(2pi/3)+sin(pi/6)sin(2pi/3) as a single trigonometric expression
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  2. #2
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    Re: Usin sum, difference, and double-angle identities

    Why don't you follow the hint in the title of the thread?
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  3. #3
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    Re: Usin sum, difference, and double-angle identities

    Hello, alejandro!

    \text{Express }\cos\tfrac{\pi}{6}\cos\tfrac{2\pi}{3}+\sin\tfrac{  \pi}{6}\sin\tfrac{2\pi}{3}\,\text{ as a single trigonometric expression.}

    Big hint: . \cos(A - B) \:=\:\cos A\cos B + \sin A\sin B
    Thanks from alejandro
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