Weird singularities/cylindrical & spherical coordinates

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SUMMARY

The discussion focuses on the behavior of the vector function expressed in cylindrical coordinates, specifically \(\frac{1}{\rho} \hat{\phi}\), which exhibits a singularity solely at the origin (\(\rho = 0\)). In contrast, when expressed in spherical coordinates as \(\frac{1}{r\sin \theta} \hat{\phi}\), the function becomes singular along the entire z-axis, occurring at \(\theta = 0\) and \(\theta = \pi\). The confusion arises from the realization that \(\rho = 0\) in cylindrical coordinates encompasses the z-axis, clarifying the apparent discrepancy in singularities between the two coordinate systems.

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If you consider the vector function (expressed in cylindrical coordinates)
<br /> \frac{1}{\rho} \hat{\phi}<br />
where \rho = \sqrt{x^2+y^2}, you notice it has a singularity at the origin ONLY. But if you express this in spherical coordinates, what you get is
<br /> \frac{1}{r\sin \theta} \hat{\phi},<br />
which is singular whenever \theta = 0 or \theta = \pi; that is, on the entire z axis! (I got this by just substituting the identities x = r\sin \theta \cos \phi and y = r \sin \theta \sin \phi into the above expression for \rho.) How can this be? I'm doing something wrong, but what?
 
Last edited:
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Uhhh...sorry, I was being really dumb. \rho = 0 includes the z-axis in cylindrical coordinates. FML.
 

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