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Homework Help: Nast y = RSin(x + a)

  1. Sep 13, 2008 #1
    1. The problem statement, all variables and given/known data
    The curve:
    y = sqrt3cosx + sinx

    a) Express the equation of the curve in the form y = RSin(x+a), where R and a are constants, R > 0 and 0 < a < pi/2

    2. Relevant equations

    3. The attempt at a solution

    I dont like these nasty R ones. Can someone walk me through please, point me in the right direction and give me tips :) Thanks :)
  2. jcsd
  3. Sep 13, 2008 #2


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    I don't like them much either, which is why I don't want you walk you through it. Start by expanding sin(x+a)=sin(x)cos(a)+cos(x)sin(a) and equate the two sides.
  4. Sep 18, 2008 #3
    well i got it

    R = 2 and a = pi/3


    y = 2Sin(x + pi/3)

    How do i find:

    i) maxiumum point of the graph?
    ii) minium point of the graph?
  5. Sep 18, 2008 #4


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    Where is the maximum point of sin(theta)? Where is x+ pi/3 equal to that theta?

    Same thing for the minimum.
  6. Sep 18, 2008 #5
    well sin moves between -1 and 1, so the maximum is when y = 2 and -2 for minimum?
  7. Sep 19, 2008 #6


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    Yes, that's right.
    Do you want to find maximum values of y or the x-coordinate corresponding to the minima or maxima of y?
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