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