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The Android Open Source Project1dc9e472009-03-03 19:28:35 -08001/* 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
The Android Open Source Project1dc9e472009-03-03 19:28:35 -080016#include "math.h"
17#include "math_private.h"
18
19static const float
20one = 1.0,
21ln2 = 6.9314718246e-01; /* 0x3f317218 */
22
23float
Elliott Hughes4088e3a2023-08-03 13:33:56 -070024acoshf(float x)
The Android Open Source Project1dc9e472009-03-03 19:28:35 -080025{
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
Elliott Hughes4088e3a2023-08-03 13:33:56 -070035 return logf(x)+ln2; /* acosh(huge)=log(2x) */
The Android Open Source Project1dc9e472009-03-03 19:28:35 -080036 } else if (hx==0x3f800000) {
37 return 0.0; /* acosh(1) = 0 */
38 } else if (hx > 0x40000000) { /* 2**28 > x > 2 */
39 t=x*x;
Elliott Hughes4088e3a2023-08-03 13:33:56 -070040 return logf((float)2.0*x-one/(x+sqrtf(t-one)));
The Android Open Source Project1dc9e472009-03-03 19:28:35 -080041 } else { /* 1<x<2 */
42 t = x-one;
Elliott Hughes4088e3a2023-08-03 13:33:56 -070043 return log1pf(t+sqrtf((float)2.0*t+t*t));
The Android Open Source Project1dc9e472009-03-03 19:28:35 -080044 }
45}