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Homework Help: Can you multiply the double angle forumla?

  1. Dec 1, 2012 #1
    1. The problem statement, all variables and given/known data
    I have sin4x, can I use the double angle forumla and make it 4sinxcosx???

    2. Relevant equations
    double angle forumla

    3. The attempt at a solution
    sin4x----> 4sinxcosx
  2. jcsd
  3. Dec 1, 2012 #2


    User Avatar

    ...try graphing both and see if they're the same.
  4. Dec 1, 2012 #3


    Staff: Mentor

    In a word, no.
    The double-angle formula says that sin(2A) = 2*sin(A)cos(A).

    When you use formulas, you need to be very careful to follow the pattern being used.
    If you write sin(4x) as sin(2(2x)), you can use the double-angle formula, replacing A in the above by 2x.
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