source: azure_iot_hub/trunk/musl-1.1.18/src/math/acoshf.c@ 388

Last change on this file since 388 was 388, checked in by coas-nagasima, 5 years ago

Azure IoT Hub Device C SDK を使ったサンプルの追加
  • Property svn:eol-style set to native
  • Property svn:keywords set to Id
  • Property svn:mime-type set to text/x-csrc
File size: 605 bytes
Line 
1#include "libm.h"
2
3#if FLT_EVAL_METHOD==2
4#undef sqrtf
5#define sqrtf sqrtl
6#elif FLT_EVAL_METHOD==1
7#undef sqrtf
8#define sqrtf sqrt
9#endif
10
11/* acosh(x) = log(x + sqrt(x*x-1)) */
12float acoshf(float x)
13{
14 union {float f; uint32_t i;} u = {x};
15 uint32_t a = u.i & 0x7fffffff;
16
17 if (a < 0x3f800000+(1<<23))
18 /* |x| < 2, invalid if x < 1 or nan */
19 /* up to 2ulp error in [1,1.125] */
20 return log1pf(x-1 + sqrtf((x-1)*(x-1)+2*(x-1)));
21 if (a < 0x3f800000+(12<<23))
22 /* |x| < 0x1p12 */
23 return logf(2*x - 1/(x+sqrtf(x*x-1)));
24 /* x >= 0x1p12 */
25 return logf(x) + 0.693147180559945309417232121458176568f;
26}
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