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Homework Help: Trigg help!

  1. Nov 25, 2008 #1
    1. The problem statement, all variables and given/known data
    Use the appropriate compound angle formula to express the following as a single trigonometric function and then determine the exact value

    2. Relevant equations
    (sin2pi/3)(cospi) + (cos2pi)(sinpi)
    sin[(2pi/3) + pi]

    3. The attempt at a solution

    first answer i got -sqrt3/2

    unsure if it's right
    Last edited: Nov 25, 2008
  2. jcsd
  3. Nov 25, 2008 #2


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    What compound angle formula are you trying to use?
  4. Nov 26, 2008 #3
    Can you please rewrite your original expression?

    Is that (sin2п/3)(cosп) + (cos2п/3)(sinп)?

    If so, as I can see you used sin(A+B) i.e sin(2п/3 + п).

    This is same as sin(п - п/3 + п) or sin(-п/3 + 2п) or -sin(п/3)

    If so, I guess your answer is correct.
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