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Basic trig phase question *sorry*

by Rudibot
Tags: basic, phase, trig
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Rudibot
#1
May11-12, 01:02 AM
P: 10
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!
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DonAntonio
#2
May11-12, 04:08 AM
P: 606
Quote Quote by Rudibot View Post
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!

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

DonAntonio
HallsofIvy
#3
May11-12, 08:07 AM
Math
Emeritus
Sci Advisor
Thanks
PF Gold
P: 39,339
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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