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1 /* @(#)e_cosh.c 5.1 93/09/24 */
3 * ====================================================
4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
6 * Developed at SunPro, a Sun Microsystems, Inc. business.
7 * Permission to use, copy, modify, and distribute this
8 * software is freely granted, provided that this notice
10 * ====================================================
12 #include <LibConfig.h>
13 #include <sys/EfiCdefs.h>
14 #if defined(LIBM_SCCS) && !defined(lint)
15 __RCSID("$NetBSD: e_cosh.c,v 1.11 2002/05/26 22:01:49 wiz Exp $");
18 #if defined(_MSC_VER) /* Handle Microsoft VC++ compiler specifics. */
19 // C4756: overflow in constant arithmetic
20 #pragma warning ( disable : 4756 )
25 * mathematically cosh(x) if defined to be (exp(x)+exp(-x))/2
26 * 1. Replace x by |x| (cosh(x) = cosh(-x)).
29 * 0 <= x <= ln2/2 : cosh(x) := 1 + -------------------
33 * ln2/2 <= x <= 22 : cosh(x) := -------------------
35 * 22 <= x <= lnovft : cosh(x) := exp(x)/2
36 * lnovft <= x <= ln2ovft: cosh(x) := exp(x/2)/2 * exp(x/2)
37 * ln2ovft < x : cosh(x) := huge*huge (overflow)
40 * cosh(x) is |x| if x is +INF, -INF, or NaN.
41 * only cosh(0)=1 is exact for finite x.
45 #include "math_private.h"
47 static const double one
= 1.0, half
=0.5, huge
= 1.0e300
;
50 __ieee754_cosh(double x
)
56 /* High word of |x|. */
61 if(ix
>=0x7ff00000) return x
*x
;
63 /* |x| in [0,0.5*ln2], return 1+expm1(|x|)^2/(2*exp(|x|)) */
67 if (ix
<0x3c800000) return w
; /* cosh(tiny) = 1 */
68 return one
+(t
*t
)/(w
+w
);
71 /* |x| in [0.5*ln2,22], return (exp(|x|)+1/exp(|x|)/2; */
72 if (ix
< 0x40360000) {
73 t
= __ieee754_exp(fabs(x
));
77 /* |x| in [22, log(maxdouble)] return half*exp(|x|) */
78 if (ix
< 0x40862E42) return half
*__ieee754_exp(fabs(x
));
80 /* |x| in [log(maxdouble), overflowthresold] */
83 ((ix
==0x408633ce)&&(lx
<=(u_int32_t
)0x8fb9f87d))) {
84 w
= __ieee754_exp(half
*fabs(x
));
89 /* |x| > overflowthresold, cosh(x) overflow */