1 /* e_acoshf.c -- float version of e_acosh.c. 2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. 3 */ 4 5 /* 6 * ==================================================== 7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 8 * 9 * Developed at SunPro, a Sun Microsystems, Inc. business. 10 * Permission to use, copy, modify, and distribute this 11 * software is freely granted, provided that this notice 12 * is preserved. 13 * ==================================================== 14 */ 15 16 #include "math.h" 17 #include "math_private.h" 18 19 static const float 20 one = 1.0, 21 ln2 = 6.9314718246e-01; /* 0x3f317218 */ 22 23 float 24 acoshf(float x) 25 { 26 float t; 27 int32_t hx; 28 GET_FLOAT_WORD(hx,x); 29 if(hx<0x3f800000) { /* x < 1 */ 30 return (x-x)/(x-x); 31 } else if(hx >=0x4d800000) { /* x > 2**28 */ 32 if(hx >=0x7f800000) { /* x is inf of NaN */ 33 return x+x; 34 } else 35 return logf(x)+ln2; /* acosh(huge)=log(2x) */ 36 } else if (hx==0x3f800000) { 37 return 0.0; /* acosh(1) = 0 */ 38 } else if (hx > 0x40000000) { /* 2**28 > x > 2 */ 39 t=x*x; 40 return logf((float)2.0*x-one/(x+sqrtf(t-one))); 41 } else { /* 1<x<2 */ 42 t = x-one; 43 return log1pf(t+sqrtf((float)2.0*t+t*t)); 44 } 45 } 46