The hyperbolic cotangent is defined as
See also Bernoulli Number, Bipolar Coordinates, Bipolar Cylindrical Coordinates, Cotangent, Fibonacci Hyperbolic Cotangent, Hyperbolic Tangent, Laplace's Equation--Toroidal Coordinates, Lebesgue Constants (Fourier Series), Prolate Spheroidal Coordinates, Surface of Revolution, Toroidal Coordinates, Toroidal Function
References
Abramowitz, M. and Stegun, C. A. (Eds.). ``Hyperbolic Functions.'' §4.5 in
Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables, 9th printing.
New York: Dover, pp. 83-86, 1972.
Spanier, J. and Oldham, K. B. ``The Hyperbolic Tangent and Cotangent Functions.''
Ch. 30 in An Atlas of Functions. Washington, DC: Hemisphere, pp. 279-284, 1987.