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| | #include "libm.h"
#if FLT_EVAL_METHOD==2
#undef sqrtf
#define sqrtf sqrtl
#elif FLT_EVAL_METHOD==1
#undef sqrtf
#define sqrtf sqrt
#endif
/* acosh(x) = log(x + sqrt(x*x-1)) */
float acoshf(float x)
{
union {float f; uint32_t i;} u = {x};
uint32_t a = u.i & 0x7fffffff;
if (a < 0x3f800000+(1<<23))
/* |x| < 2, invalid if x < 1 or nan */
/* up to 2ulp error in [1,1.125] */
return log1pf(x-1 + sqrtf((x-1)*(x-1)+2*(x-1)));
if (a < 0x3f800000+(12<<23))
/* |x| < 0x1p12 */
return logf(2*x - 1/(x+sqrtf(x*x-1)));
/* x >= 0x1p12 */
return logf(x) + 0.693147180559945309417232121458176568f;
}
|