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Homework Help: Calculate phase between sine waves given the time difference

  1. Sep 4, 2009 #1
    1. The problem statement, all variables and given/known data

    How do i find the phase between sine waves knowing the time difference between each?

    Equation for the main function is 3cos(30t - Pi/2)
    The smaller sine wave is of the same frequency when is settles in a steady state.

    2. Relevant equations

    i thought it was
    time difference * 2*Pi*f = phase difference in radians

    3. The attempt at a solution
    30 = 2*Pi * f

    -.05*30 = 1.5 radians
    -1.5*360/(2Pi) = -85.94 degrees

    MATLAB give the phase difference as -76.3995 degrees
    this is equivalent to -0.0444474274 difference in seconds

    Is this just due to rounding error??
    Last edited by a moderator: Apr 24, 2017
  2. jcsd
  3. Sep 4, 2009 #2
    i think i just answered my own question... 2.57 seconds for the larger sine wave still give an amplitude of 3.. In this case the time difference is -0.04.

    it definitely is due to rounding
  4. Sep 4, 2009 #3


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    Staff Emeritus
    Science Advisor
    Homework Helper

    You did it right, but note that the 0.05s time difference contains just one significant figure.
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