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Homework Help: A Odd Radian Question.

  1. Aug 25, 2009 #1
    1. The problem statement, all variables and given/known data
    Consider the function y=sin2x +cos3x.

    a.] Find a Value for the y if x= pye [Or who how ever it is spelled. 3.141592654]

    b.] Find y if x=0.3 Radians.

    c.] What is a period of this function? Show how you obtain this answer.

    3. The attempt at a solution

    No attempt since I have never come across these types of question in Radians before.
  2. jcsd
  3. Aug 25, 2009 #2


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    Science Advisor
    Homework Helper

    Hi Venito! :smile:

    (have a pi: π :wink:)
    π radians = 180º …

    if you're not used to radians, do it in degrees, and convert using the 180/π factor. :wink:
  4. Aug 25, 2009 #3
    I am use to radians. Just not these. So use degrees. Okay I will give it a try.

  5. Aug 25, 2009 #4


    Staff: Mentor

    The period of sin(2x) is π radians. The period of cos(3x) is 2π/3 radians. The period of the sum of these two functions is the smallest interval that is evenly divisible by both π and 2π/3.

    By the way, we spell the name of this Greek letter as pi. I'm guessing that you're Italian, and it is spelled the same way in Italian.
  6. Aug 25, 2009 #5


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    Science Advisor

    You certainly should know that [itex]sin(2\pi)= 0[/itex] and [itex]cos(3\pi)= -1[/itex].

    This is not going to be any simple value. Use a calculator.

    What is the period of sin(2x)? What is the cos(3x)? What is the least common multiple of those two periods? Do you see why that is the period of y?

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