2 cosh - hyperbolic cosine
9 eps nonzero real, defaults to epsilon()
14 Calculate the cosh of x to the nearest or next to nearest multiple of
15 epsilon, with absolute error less than .75 * abs(eps).
17 cosh(x) = (exp(x) + exp(-x))/2
20 > print cosh(1, 1e-5), cosh(1, 1e-10), cosh(1, 1e-15), cosh(1, 1e-20)
21 1.54308 1.5430806348 1.543080634815244 1.54308063481524377848
27 NUMBER *qcosh(NUMBER *x, NUMBER *eps)
30 sinh, tanh, sech, csch, coth, epsilon