mirror of
https://gitea.nishi.boats/pyrite-dev/milsko
synced 2025-12-31 06:30:52 +00:00
7f523a3d76
git-svn-id: http://svn2.nishi.boats/svn/milsko/trunk@557 b9cfdab3-6d41-4d17-bbe4-086880011989
56 lines
1.5 KiB
C
56 lines
1.5 KiB
C
|
|
/* @(#)e_acosh.c 1.3 95/01/18 */
|
|
/*
|
|
* ====================================================
|
|
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
|
|
*
|
|
* Developed at SunSoft, a Sun Microsystems, Inc. business.
|
|
* Permission to use, copy, modify, and distribute this
|
|
* software is freely granted, provided that this notice
|
|
* is preserved.
|
|
* ====================================================
|
|
*
|
|
*/
|
|
|
|
/* __fdlibm_acosh(x)
|
|
* Method :
|
|
* Based on
|
|
* acosh(x) = log [ x + sqrt(x*x-1) ]
|
|
* we have
|
|
* acosh(x) := log(x)+ln2, if x is large; else
|
|
* acosh(x) := log(2x-1/(sqrt(x*x-1)+x)) if x>2; else
|
|
* acosh(x) := log1p(t+sqrt(2.0*t+t*t)); where t=x-1.
|
|
*
|
|
* Special cases:
|
|
* acosh(x) is NaN with signal if x<1.
|
|
* acosh(NaN) is NaN without signal.
|
|
*/
|
|
|
|
#include "math.h"
|
|
|
|
static const double
|
|
one = 1.0,
|
|
ln2 = 6.93147180559945286227e-01; /* 0x3FE62E42, 0xFEFA39EF */
|
|
|
|
double __fdlibm_acosh(double x) {
|
|
double t;
|
|
int hx;
|
|
hx = __HI(x);
|
|
if(hx < 0x3ff00000) { /* x < 1 */
|
|
return (x - x) / (x - x);
|
|
} else if(hx >= 0x41b00000) { /* x > 2**28 */
|
|
if(hx >= 0x7ff00000) { /* x is inf of NaN */
|
|
return x + x;
|
|
} else
|
|
return __fdlibm_log(x) + ln2; /* acosh(hugev)=log(2x) */
|
|
} else if(((hx - 0x3ff00000) | __LO(x)) == 0) {
|
|
return 0.0; /* acosh(1) = 0 */
|
|
} else if(hx > 0x40000000) { /* 2**28 > x > 2 */
|
|
t = x * x;
|
|
return __fdlibm_log(2.0 * x - one / (x + sqrt(t - one)));
|
|
} else { /* 1<x<2 */
|
|
t = x - one;
|
|
return log1p(t + sqrt(2.0 * t + t * t));
|
|
}
|
|
}
|