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from basic expressions to quarterions


a two dimensional shape can be simplified as a collection of points. the points can then be complex number represented as well as a well chosen origin for convenient point rotations. the shape is then effectively rotated.

the creation of a rotating shape using complex numbers is quite interesting as well as useful. for example in robotics in real-time navigation, the CORDIC FAQ can serve as a super quick means of rotating a spacial image.

a google search with keywords "complex number rotation" (no quotes) found the following diverse references

For Kids:

More Complex Makes Simple!
http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/info/signals/complex/cmplx.html
Jim Lesurf is certainly having fun with rotating animations.

Complex number - From Wikipedia, the free encyclopedia.
http://en.wikipedia.org/wiki/Complex_number

Complex Numbers, Trig & Vectors
http://whyslopes.com/etc/ComplexNumbers


Advanced:

Using Quaternions to Represent Rotation By: Laura Downs http://www.genesis3d.com/~kdtop/Quaternions-UsingToRepresentRotation.htm
quaternions are a kind of "3D" complex number and great to represent dynamic spacial operations such as cartesian coordinates for trajectory paths (think missile).

Complex numbers and similarity constants
http://www.math.okstate.edu/mathdept/dynamics/lecnotes/node30.html
complex numbers generate sphinx figures and form a neat spiral known as a loxodrome

CORDIC FAQ by Grant R. Griffin
http://www.dspguru.com/info/faqs/cordic2.htm
rotations are done using algorithm quick binary shifts.

Cycloids
http://www.cut-the-knot.com/pythagoras/cycloids.shtml
the term cycloids is also used to refer to epicycloids and hypocycloids.

Cycloids
Epicycloids
Hypocycloids