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git.ipfire.org Git - thirdparty/glibc.git/blob - sysdeps/ieee754/ldbl-128ibm/e_coshl.c
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 * ====================================================
15 * mathematically cosh(x) if defined to be (exp(x)+exp(-x))/2
16 * 1. Replace x by |x| (cosh(x) = cosh(-x)).
19 * 0 <= x <= ln2/2 : cosh(x) := 1 + -------------------
23 * ln2/2 <= x <= 22 : cosh(x) := -------------------
25 * 22 <= x <= lnovft : cosh(x) := exp(x)/2
26 * lnovft <= x <= ln2ovft: cosh(x) := exp(x/2)/2 * exp(x/2)
27 * ln2ovft < x : cosh(x) := huge*huge (overflow)
30 * cosh(x) is |x| if x is +INF, -INF, or NaN.
31 * only cosh(0)=1 is exact for finite x.
35 #include "math_private.h"
37 static const long double one
= 1.0L, half
=0.5L, huge
= 1.0e300L
;
40 __ieee754_coshl (long double x
)
45 /* High word of |x|. */
46 GET_LDOUBLE_MSW64(ix
,x
);
47 ix
&= 0x7fffffffffffffffLL
;
50 if(ix
>=0x7ff0000000000000LL
) return x
*x
;
52 /* |x| in [0,0.5*ln2], return 1+expm1(|x|)^2/(2*exp(|x|)) */
53 if(ix
<0x3fd62e42fefa39efLL
) {
54 t
= __expm1l(fabsl(x
));
56 if (ix
<0x3c80000000000000LL
) return w
; /* cosh(tiny) = 1 */
57 return one
+(t
*t
)/(w
+w
);
60 /* |x| in [0.5*ln2,22], return (exp(|x|)+1/exp(|x|)/2; */
61 if (ix
< 0x4036000000000000LL
) {
62 t
= __ieee754_expl(fabsl(x
));
66 /* |x| in [22, log(maxdouble)] return half*exp(|x|) */
67 if (ix
< 0x40862e42fefa39efLL
) return half
*__ieee754_expl(fabsl(x
));
69 /* |x| in [log(maxdouble), overflowthresold] */
70 if (ix
< 0x408633ce8fb9f87dLL
) {
71 w
= __ieee754_expl(half
*fabsl(x
));
76 /* |x| > overflowthresold, cosh(x) overflow */
79 strong_alias (__ieee754_coshl
, __coshl_finite
)