source:
azure_iot_hub/trunk/musl-1.1.18/src/math/acosh.c
Last change on this file was 389, checked in by , 5 years ago | |
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File size: 569 bytes |
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1 | #include "libm.h" |
2 | |
3 | #if FLT_EVAL_METHOD==2 |
4 | #undef sqrt |
5 | #define sqrt sqrtl |
6 | #endif |
7 | |
8 | /* acosh(x) = log(x + sqrt(x*x-1)) */ |
9 | double acosh(double x) |
10 | { |
11 | union {double f; uint64_t i;} u = {.f = x}; |
12 | unsigned e = u.i >> 52 & 0x7ff; |
13 | |
14 | /* x < 1 domain error is handled in the called functions */ |
15 | |
16 | if (e < 0x3ff + 1) |
17 | /* |x| < 2, up to 2ulp error in [1,1.125] */ |
18 | return log1p(x-1 + sqrt((x-1)*(x-1)+2*(x-1))); |
19 | if (e < 0x3ff + 26) |
20 | /* |x| < 0x1p26 */ |
21 | return log(2*x - 1/(x+sqrt(x*x-1))); |
22 | /* |x| >= 0x1p26 or nan */ |
23 | return log(x) + 0.693147180559945309417232121458176568; |
24 | } |
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