negative polar axis

[Erik Max Francis]

Steve Holden wrote:

> About the best interpretation I can think of is to add 180 degrees to 
> the angle and reverse the sign of the magnitude, but this would be a 
> hack. Where are those coordinates coming from?

Well, sometimes in polar coordinates (r, theta), r is allowed to be 
negative.  The usual translation from polar to Cartesian coordinates 
makes this meaningful, albeit weird, so in effect the resulting 
positions are just reflections around the origin.

Which I suppose is what the original poster was asking about, but it's 
still not clear.

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