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Homework Help: Graph analysis with trig involved

  1. Dec 22, 2009 #1
    1. The problem statement, all variables and given/known data
    given: y=sin2x-2sinx

    2. Relevant equations

    3. The attempt at a solution

    i already found the roots of the equation, i also found the first and second derivatives which are 2cosx2-2cosx and -4sin2x+2sinx. however, i do not know how to find the roots for these equations in order to do mins and maxes and inflection pt. is it true that the inflection piont is zero, cuz thats how someone said to do it, but would that mean no concavity at all? and the original is differentiable and continuous correct? also, how wouuld i find the domain and range of this?
  2. jcsd
  3. Dec 22, 2009 #2


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    Homework Helper

    For the first derivative, use the double angle formula

    cos2x=2cos2x-1 = 1-2sin2x

    Solve for x and sub that into the expression for y''.
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