q-Cosine
The q-Analog of the Cosine function, as advocated by R. W. Gosper, is defined by
where
is a Theta Function and 
is defined via
This is a period
, Even Function of unit amplitude with double and triple angle formulas and addition formulas whichare analogous to ordinary Sine and Cosine. For example,
where
is the q-Sine, and 
is q-Pi. The 
-cosine also satisfies
See also q-Factorial, q-Sine
References
Gosper, R. W. ``Experiments and Discoveries in -Trigonometry.'' Unpublished manuscript.
- Pentagonal Number
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