25 lines
579 B
C
25 lines
579 B
C
#include "libc/math/libm.h"
|
|
|
|
#if FLT_EVAL_METHOD==2
|
|
#undef sqrt
|
|
#define sqrt sqrtl
|
|
#endif
|
|
|
|
/* acosh(x) = log(x + sqrt(x*x-1)) */
|
|
double acosh(double x)
|
|
{
|
|
union {double f; uint64_t i;} u = {.f = x};
|
|
unsigned e = u.i >> 52 & 0x7ff;
|
|
|
|
/* x < 1 domain error is handled in the called functions */
|
|
|
|
if (e < 0x3ff + 1)
|
|
/* |x| < 2, up to 2ulp error in [1,1.125] */
|
|
return log1p(x-1 + sqrt((x-1)*(x-1)+2*(x-1)));
|
|
if (e < 0x3ff + 26)
|
|
/* |x| < 0x1p26 */
|
|
return log(2*x - 1/(x+sqrt(x*x-1)));
|
|
/* |x| >= 0x1p26 or nan */
|
|
return log(x) + 0.693147180559945309417232121458176568;
|
|
}
|