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Trig : Simplify?

  1. Apr 24, 2012 #1
    1. The problem statement, all variables and given/known data

    Simplify the expression Cos(6θ)
    Simplify means - the angle for all trigonometric functions in your answer is to be only θ.
    Simplify in terms of sines and cosines
    Simplify in terms of cosines only
    Simplify in terms of sines only

    2. Relevant equations

    Basic Trig Identities (attachment)

    3. The attempt at a solution

    Im kind of lost to tell you the truth...
    Maybe im over thinking the difficulty of the problem and its a lot simpler then what I am making it out to be.

    ?? cos(2θ+2θ+2θ) ??

    Just help me get started on this problem.
    Guide me through the first couple of steps
     

    Attached Files:

    Last edited: Apr 24, 2012
  2. jcsd
  3. Apr 24, 2012 #2

    HallsofIvy

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    Staff Emeritus
    Science Advisor

    Do equations have to be given? It seems to me that whoever gave you this problem expects you to know some basic trig identities yourself.

    I would think that things like
    sin(a+ b)= sin(a)cos(b)+ cos(a)sin(b)
    cos(a+ b)= cos(a)cos(b)- sin(a)sin(b)
    sin(2a)= 2sin(a)cos(a)
    cos(2a)= cos^2(a)- sin^2(a)
    would be very relevant!

    For example, what do they give for
    sin(3a)= sin(2a+ a)?
     
  4. Apr 24, 2012 #3
    well the problem itself was did not come with identities.
    what the textbook contains in terms of what we have covered in class i guess are the equations.

    Added attachment
     
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