Trailing-Edge
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PDP-10 Archives
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SRI_NIC_PERM_FS_1_19910112
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c/lib5/pml/dacosh.c
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/*
* +++ NAME +++
*
* DACOSH Double precision hyperbolic arc cosine
*
* +++ INDEX +++
*
* DACOSH
* machine independent routines
* math libraries
*
* +++ DESCRIPTION +++
*
* Returns double precision hyperbolic arc cosine of double precision
* floating point number.
*
* +++ USAGE +++
*
* double dacosh(x)
* double x;
*
* +++ REFERENCES +++
*
*
* +++ RESTRICTIONS +++
*
* The range of the ACOSH function is all real numbers greater
* than or equal to 1.0 however large arguments may cause
* overflow in the x squared portion of the function evaluation.
*
* For precision information refer to documentation of the
* floating point library primatives called.
*
* +++ PROGRAMMER +++
*
* Fred Fish
* Goodyear Aerospace Corp, Arizona Div.
* (602) 932-7000 work
* (602) 894-6881 home
*
* +++ INTERNALS +++
*
* Computes DACOSH(X) from:
*
* 1. If X < 1.0 then report illegal
* argument and return zero.
*
* 2. If X > DSQRT(MAX_POS_DBLF) then
* set X = DSQRT(MAX_POS_DBLF and
* continue after reporting overflow.
*
* 3. DACOSH(X) = LN [X+DSQRT(X**2 - 1)]
*
* ---
*/
/*)LIBRARY
*/
#include <stdio.h>
#include "c:pmluse.h"
#include "pml.h"
double dacosh(x)
double x;
{
double dln(), dsqrt();
if (x < 1.0) {
pmlerr(DACOSH_BADARG);
return(0.0);
} else {
if (x > DSQRT_MPDF) {
pmlerr(DACOSH_OVERFLOW);
x = DSQRT_MPDF;
}
return ( dln(x + dsqrt(x*x - 1.0)) );
}
}