calculate magnitude and phase

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10 comments, last by alvaro 14 years, 2 months ago
Quote:Original post by acp693
Thanks, That's what I first thought, however consider the simpler case of
x direction vector= Magnitude 6, phase 0 degrees, (6+0i)
y direction vector= magnitude 6, phase 90 degrees,(0+6i)


Oh, your problem is not the problem I thought you had...

Anyway, here's how I'd think about it. From my last post you see how you can represent a phase-shifted sinusoid either in "polar" (magitude/phase), or "cartesian" (cosine term, sine term) form. Well that means that you can write your point (x,y)(t) as,

[ x(t) ]   [ A1   B1 ] [ cos(t) ][      ] = [         ] [        ][ y(t) ]   [ A2   B2 ] [ sin(t) ]


or more simply, just

p(t) = M u(t)

where u(t) is a unit vector for all time, and p=(x,y).

What unit vector u maximizes the norm of the expression "M u" ? Simply the one corresponding to the largest singular value of M! Equivalently: The eigenvector corresponding to the largest eigenvalue of MT M.
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I was about to post the exact same thing Emergent posted, only less clearly exposed. :)

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