| #include "libm.h" | |
| /* acosh(x) = log(x + sqrt(x*x-1)) */ | |
| float acoshf(float x) | |
| { | |
| union {float f; int32_t i;} u = {.f = x}; | |
| if (u.i < 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 (u.i < 0x3f800000+(12<<23)) | |
| /* x < 0x1p12 */ | |
| return logf(2*x - 1/(x+sqrtf(x*x-1))); | |
| /* x >= 0x1p12 */ | |
| return logf(x) + 0.693147180559945309417232121458176568f; | |
| } |