Discussion in 'Homework Help' started by daunus, May 7, 2009.

1. ### daunus Thread Starter New Member

May 7, 2009
1
0
Hi Im new to these forums but hopefull ill hang around for a while,

Determine which waveform in each pair is lagging and by how much

a)6cos(2pi60t-9°) & -6cos(2pi60t+9°)

b)cos(t-100°) & -cos (t-100°)

c)700cos(t-pi) & 700cos(t-3.14°) ---- here I think first waveform laggs by 176.86 °

does a negative amplitude make any diffrence?

2. ### SawabyPlus Member

Feb 27, 2009
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phase written between the parentheses may be misleading if the amplitude is not +ve, for real systems of course.
you should just drop the sign and add a phase of +/-pi to compensate. put the resultant phase in the principal form. and u know the rest, like you've done in part c.

3. ### KL7AJ AAC Fanatic!

Nov 4, 2008
2,208
427

Yes....this is why there is always a phase ambiguity problem with things like phase locked loops....is it leading by 90 or lagging by 270?

Eric

4. ### mik3 Senior Member

Feb 4, 2008
4,846
70
The minus sign means that the waveform is also shifted by 180 degrees because cos(θ+180)=-cos(θ).

Thus

-Acos(ωt+θ)=Acos(ωt+θ+180)