## Cotangent

The function defined by , where is the Tangent. The Maclaurin Series for cot is

where is a Bernoulli Number.

It is known that, for , is rational only for .

Abramowitz, M. and Stegun, C. A. (Eds.). Circular Functions.'' §4.3 in Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables, 9th printing. New York: Dover, pp. 71-79, 1972.
Spanier, J. and Oldham, K. B. The Tangent and Cotangent Functions.'' Ch. 34 in An Atlas of Functions. Washington, DC: Hemisphere, pp. 319-330, 1987.