y1Bessel function of second kind of order one.
double x, y, y1();
y = y1(x);
Returns a Bessel function of the second kind of order one of the argument.
The domain is divided into the intervals [0, 8] and (8, infinity). In the first interval a 25 term Chebyshev expansion is used, and a call to j1() is required. In the second, the asymptotic trigonometric representation is employed using two rational functions of degree 5/5.
arithmetic domain # trials peak rms
DEC 0, 30 10000 8.6e-17 1.3e-17
IEEE 0, 30 30000 1.0e-15 1.3e-16
(error criterion relative when |y1| > 1).