cosh

Hyperbolic cosine.

SYNOPSIS:

double x, y, cosh();
y = cosh(x);

DESCRIPTION:

Returns the hyperbolic cosine of an argument in the range MINLOG to MAXLOG.

cosh(x) = (exp(x) + exp(-x))/2.

ACCURACY:
                      Relative error:
arithmetic   domain     # trials      peak         rms
    DEC       +- 88       50000       4.0e-17     7.7e-18
    IEEE     +-MAXLOG     30000       2.6e-16     5.7e-17

ERROR MESSAGES:

message         condition      value returned
overflow        |x| > MAXLOG       MAXNUM