First we show that is a holomorphic function,
and therefore is a angle-conform map.
This means a rectengular grid of horizontzal and vertical lines in a
family of paraboli and circles are mapped in circles (see
Figure 6)
Figure 6:
The upper left picture shows a rectengular grid of the relevant
piece of the complex plane. The upper right shows the mapping of the grid
with respect to . The lower pictures show the same process for
a polar grid
Theorem 9
The map is a holomorphic map.
Proof.
You can separate the real and imaginary part of
as
(1)
This yields that the Cauchy-Riemann differential equations are
true and therefore is holomorph.
Theorem 10 (The cardiode is part of the set)
The filled cardiodic curve
(c)
is part of the mandelbrot set. The interior of this curve contains
Lyapunov-stable fixed points and the border contains neutral
fixed points of the map
for fixed