Möbius transformations are continuous on the Riemann sphere
The complex plane together with the point at infinity (      ) make up the Riemann sphere. The North pole of the Riemann sphere corresponds to      , the South pole corresponds to the origin of the complex plane and the equator corresponds to the unit circle.
In order to show that Möbius transformations are continuous on the Riemann sphere, we must look at two cases:
1) If c = 0,
 and
2) If c ≠ 0,
    
   then           and
Therefore, M(z) is continuous on the extended z plane, or Riemann sphere.