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Sin cos waves

  1. Dec 25, 2011 #1
    In what kind of cases do u we formulate the equation type x=Asin(wt+phi) or x=Acos(wt+phi)...and if for example we use it to define the position of some thing in motion when do we know when to use cos and when to use sin...?
  2. jcsd
  3. Dec 25, 2011 #2


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    Science Advisor
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    It doesn't really matter which you use. The only difference is what position on the wave corresponds to phi = 0. A sin(wt+phi + pi/2) = A cos(wt+phi)
  4. Dec 25, 2011 #3


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    Staff: Mentor

    It depends on the initial conditions for your specific situation. If the object is at x = 0 when t = 0, then it's easiest to use a sine wave. If the object is at x = maximum (i.e. the amplitude) when t = 0 then it's easiest to use a cosine wave.

    However, as AlephZero noted, you can use either kind of wave in any case, by including an appropriate phase factor.
  5. Dec 25, 2011 #4
    and we find the phase factor by setting x=0, right?
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