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/* ef_acosh.c -- float version of e_acosh.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 "fdlibm.h"

#ifdef __STDC__

static const float

#else

static float

#endif

one     = 1.0,

ln2     = 6.9314718246e-01;  /* 0x3f317218 */

#ifdef __STDC__

        float acoshf(float x)

#else

        float acoshf(x)

        float x;

#endif

{

        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;

            } else

                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((float)2.0*x-one/(x+sqrtf(t-one)));

        } else {                        /* 1<x<2 */

            t = x-one;

            return log1pf(t+sqrtf((float)2.0*t+t*t));

        }

}