(3) ([30%]) Consider a regular surface S where and the inversion Φ :R3\ given by
Compare the mean curvature and the Gauss urvatures of S and of the image
surface S' = Φ(S). More precisely, show that
and where N(p) is the unit
normal of S at p, H'(Φ(p) is the mean curvature of s' at Φ(p), K'(Φ(p) is the
Gauss curvature of S' at Φ(p).