/* acosh(x) = log (x + sqrt(x * x - 1)) */
long double acoshl (long double x)
{
if (isnan (x))
return x;
if (x < 1.0L)
{
errno = EDOM;
return nanl("");
}
if (x > 0x1p32L)
/* Avoid overflow (and unnecessary calculation when
sqrt (x * x - 1) == x).
The M_LN2 define doesn't have enough precison for
long double so use this one. GCC optimizes by replacing
the const with a fldln2 insn. */
return __fast_logl (x) + 6.9314718055994530941723E-1L;
/* Since x >= 1, the arg to log will always be greater than
the fyl2xp1 limit (approx 0.29) so just use logl. */
return __fast_logl (x + __fast_sqrtl((x + 1.0L) * (x - 1.0L)));
}
/* asinh(x) = copysign(log(fabs(x) + sqrt(x * x + 1.0)), x) */
long double asinhl(long double x)
{
long double z;
if (!isfinite (x))
return x;
z = fabsl (x);
/* Avoid setting FPU underflow exception flag in x * x. */
#if 0
if ( z < 0x1p-32)
return x;
#endif
/* Use log1p to avoid cancellation with small x. Put
x * x in denom, so overflow is harmless.
asinh(x) = log1p (x + sqrt (x * x + 1.0) - 1.0)
= log1p (x + x * x / (sqrt (x * x + 1.0) + 1.0)) */
z = __fast_log1pl (z + z * z / (__fast_sqrtl (z * z + 1.0L) + 1.0L));
return ( x > 0.0 ? z : -z);
}
