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Basic trig phase question *sorry*

  1. May 11, 2012 #1
    I'm a bit rusty..

    I have a cosine
    y = cos(2*pi*f*t)
    If I want to advance the cosine by say 90 degrees
    y = cos(2*pi*f*t + pi/2)

    but..
    this waveform has f cycles per 2*pi*t..so won't I be advancing the phase by f*pi/2?
    someone pls straigthen me out - I'm working with Matlab indexes and I'm getting confused!
     
  2. jcsd
  3. May 11, 2012 #2

    I'm not really sure what're you asking, but [itex]\,\,\displaystyle{\cos \left(\alpha+\frac{\pi}{2}\right)=-\sin (\alpha)}\,\,[/itex]

    DonAntonio
     
  4. May 11, 2012 #3

    HallsofIvy

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    Staff Emeritus
    Science Advisor

    cos(2*piZ*f*t+ pi/2) is different from cos(2*pi*f(t+ pi/2)). The first just translates the wave by pi/2, the second translates by pi^2*f.
     
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