Trailing-Edge
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PDP-10 Archives
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SRI_NIC_PERM_FS_1_19910112
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kccdist/lib/math/cosh.c
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/*
* +++ NAME +++
*
* COSH Double precision hyperbolic cosine
*
* +++ INDEX +++
*
* COSH
* machine independent routines
* math libraries
*
* +++ DESCRIPTION +++
*
* Returns double precision hyperbolic cosine of double precision
* floating point number.
*
* +++ USAGE +++
*
* double cosh(x)
* double x;
*
* +++ REFERENCES +++
*
* Fortran IV plus user's guide, Digital Equipment Corp. pp B-4
*
* +++ RESTRICTIONS +++
*
* Inputs greater than LN(MAX_POS_DBLF) result in overflow.
* Inputs less than LN(MIN_POS_DBLF) result in underflow.
*
* For precision information refer to documentation of the
* floating point library routines called.
*
* +++ PROGRAMMER +++
*
* Fred Fish
* Goodyear Aerospace Corp, Arizona Div.
* (602) 932-7000 work
* (602) 894-6881 home
*
* Updated Dec 85 for inclusion in standard math library. This routine
* now conforms with the description of the cosh function as defined in
* Harbison & Steele's "C: A Reference Manual", section 11.3.8
*
* +++ INTERNALS +++
*
* Computes hyperbolic cosine from:
*
* cosh(X) = 0.5 * (exp(X) + exp(-X))
*
* ---
*/
#include "math.h"
#include "errno.h"
double cosh(x)
double x;
{
double exp();
if (x > LN_MAXPOSDBL || x < LN_MINPOSDBL) {
errno = ERANGE;
return MAX_POS_DBLF;
} else return 0.5 * (exp(x) + exp(-x));
}