To find the formula for this combinaton of three reflections
requires very little knowledge of complex numbers. All you have to
do is to combine the complex maps as you combine functions.. The
example shows the power of complex numbers as a tool for working
with transformations in the plane.
In the problem
Complex Rotations you see another
examle of using complex numbers for work with
transformations.
The problem
The Matrix introduces the idea of
using matrices for work with transformations.The use of 2 by 2
matrices is efficient for transformations which have a fixed
point, usually taken to be the origin. Complex numbers have the
advantage that they also handle translations.
The problems
Rots and Refs and
Reflect Again are examples of the use
of matrices for work with transformations.
This problem is about combinations of reflections. The problem
Reflect Again uses matrices to show
that the combination of two reflections in intersecting mirror
lines gives a rotation.