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/* origin: FreeBSD /usr/src/lib/msun/src/e_acoshf.c */
/*
* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
*/
/*
* ====================================================
* 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.
* ====================================================
*/
#include "libm.h"
static const float
one = 1.0,
ln2 = 6.9314718246e-01; /* 0x3f317218 */
float acoshf(float x)
{
float t;
int32_t hx;
GET_FLOAT_WORD(hx, x);
if (hx < 0x3f800000) { /* x < 1 */
return (x-x)/(x-x);
} else if (hx >= 0x4d800000) { /* x > 2**28 */
if (hx >= 0x7f800000) /* x is inf of NaN */
return x + x;
return logf(x) + ln2; /* acosh(huge)=log(2x) */
} else if (hx == 0x3f800000) {
return 0.0; /* acosh(1) = 0 */
} else if (hx > 0x40000000) { /* 2**28 > x > 2 */
t = x*x;
return logf(2.0f*x - one/(x+sqrtf(t-one)));
} else { /* 1 < x < 2 */
t = x-one;
return log1pf(t + sqrtf(2.0f*t+t*t));
}
}
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