Comments by "EebstertheGreat" (@EebstertheGreat) on "Inversion (extra) - Numberphile" video.

  1.  @oscargr_  No, like, you extend the real plane to add a single point at infinity. That makes the plane an infinitely large sphere. I guess this is called the real projective plane. A neighborhood of infinity contains all points outside of some disk centered at the origin.
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  2. The special case of a circle that passes through the center can be removed if the center of inversion maps to a point at infinity, since any circle passing through the center must invert to a circle that passes through the point at infinity, making it a circle of infinite radius (i.e. a line).
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  3.  @oscargr_  The center of inversion maps to the point at infinity.
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  4.  @DanielFrance81  Yeah, you're right.
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