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Homework Help: How to determine the point of intersection of sine and cosine?

  1. Mar 14, 2007 #1
    1. The problem statement, all variables and given/known data

    Im not sure how to start this question: determine the points of intersection between [tex]y=sin x[/tex] and [tex]y=cos 2 x[/tex] for x between 0 and pi.

    3. The attempt at a solution

    First thing that comes to mind is the eqaute the two, but i dont know how that helps me?
  2. jcsd
  3. Mar 14, 2007 #2


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    It should help you. And the identities regarding the sin and cos functions should help you more...
  4. Mar 14, 2007 #3


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    Particularly an indentity that says cos(2x) is equal to something.
  5. Mar 14, 2007 #4
    thanks ive got it now, but is the only point of intersection in the range at [tex]\frac{\pi}{2}[/tex]? i suppose i could graph it to be sure...
    Last edited: Mar 14, 2007
  6. Mar 14, 2007 #5

    Gib Z

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  7. Mar 14, 2007 #6
    okay, i was solving incorrectly, they will also both be at [tex]30^{o}[/tex]. i also assumed i would get a "nice" number. thanks.
    Last edited: Mar 14, 2007
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