2 coth - hyperbolic cotangent
9 eps nonzero real, defaults to epsilon()
14 Calculate the coth of x to a multiple of eps with error less in
15 absolute value than .75 * eps.
17 coth(x) = (exp(2*x) + 1)/(exp(2*x) - 1)
20 > print coth(1, 1e-5), coth(1, 1e-10), coth(1, 1e-15), coth(1, 1e-20)
21 1.31304 1.3130352855 1.313035285499331 1.31303528549933130364
27 NUMBER *qcoth(NUMBER *x, NUMBER *eps)
30 sinh, cosh, tanh, sech, csch, epsilon