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asin
Inverse circular sine.SYNOPSIS:
double x, y, asin();
y = asin(x);
DESCRIPTION:
Returns the radian angle between -pi/2 and +pi/2 whose sine is x.
A rational function of the form x + x**3 P(x**2)/Q(x**2) is used for |x| in the interval [0, 0.5]. If |x| > 0.5 it is transformed by the identity:
asin(x) = pi/2 - 2 asin(sqrt((1-x)/2)).
ACCURACY:
Relative error:
arithmetic domain # trials peak rms
DEC -1, 1 40000 2.6e-17 7.1e-18
IEEE -1, 1 10^6 1.9e-16 5.4e-17
ERROR MESSAGES:
message condition value returned
domain |x| > 1 NAN