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/* @(#)w_acosh.c 5.1 93/09/24 */
/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunPro, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*
*/
/*
FUNCTION
<<acosh>>, <<acoshf>>---inverse hyperbolic cosine
INDEX
acosh
INDEX
acoshf
SYNOPSIS
#include <math.h>
double acosh(double <[x]>);
float acoshf(float <[x]>);
DESCRIPTION
<<acosh>> calculates the inverse hyperbolic cosine of <[x]>.
<<acosh>> is defined as
@ifnottex
. log(<[x]> + sqrt(<[x]>*<[x]>-1))
@end ifnottex
@tex
$$ln\Bigl(x + \sqrt{x^2-1}\Bigr)$$
@end tex
<[x]> must be a number greater than or equal to 1.
<<acoshf>> is identical, other than taking and returning floats.
RETURNS
<<acosh>> and <<acoshf>> return the calculated value. If <[x]>
less than 1, the return value is NaN and <<errno>> is set to <<EDOM>>.
You can change the error-handling behavior with the non-ANSI
<<matherr>> function.
PORTABILITY
Neither <<acosh>> nor <<acoshf>> are ANSI C. They are not recommended
for portable programs.
QUICKREF
ansi svid posix rentrant
acos n,n,n,m
acosf n,n,n,m
MATHREF
acosh, NAN, arg,DOMAIN,EDOM
acosh, < 1.0, NAN,DOMAIN,EDOM
acosh, >=1.0, acosh(arg),,,
MATHREF
acoshf, NAN, arg,DOMAIN,EDOM
acoshf, < 1.0, NAN,DOMAIN,EDOM
acoshf, >=1.0, acosh(arg),,,
*/
/*
* wrapper acosh(x)
*/
#include "fdlibm.h"
#include <errno.h>
#ifndef _DOUBLE_IS_32BITS
#ifdef __STDC__
double acosh(double x) /* wrapper acosh */
#else
double acosh(x) /* wrapper acosh */
double x;
#endif
{
#ifdef _IEEE_LIBM
return __ieee754_acosh(x);
#else
double z;
struct exception exc;
z = __ieee754_acosh(x);
if(_LIB_VERSION == _IEEE_ || isnan(x)) return z;
if(x<1.0) {
/* acosh(x<1) */
exc.type = DOMAIN;
exc.name = "acosh";
exc.err = 0;
exc.arg1 = exc.arg2 = x;
exc.retval = 0.0/0.0;
if (_LIB_VERSION == _POSIX_)
errno = EDOM;
else if (!matherr(&exc)) {
errno = EDOM;
}
if (exc.err != 0)
errno = exc.err;
return exc.retval;
} else
return z;
#endif
}
#endif /* defined(_DOUBLE_IS_32BITS) */
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