y1(x) = <ufunc 'y1'>¶
Bessel function of the second kind of order 1.
x : array_like
Y : ndarray
Value of the Bessel function of the second kind of order 1 at x.
The domain is divided into the intervals [0, 8] and (8, infinity). In the first interval a 25 term Chebyshev expansion is used, and computing \(J_1\) (the Bessel function of the first kind) is required. In the second, the asymptotic trigonometric representation is employed using two rational functions of degree 5/5.
This function is a wrapper for the Cephes [R591] routine
[R591] (1, 2) Cephes Mathematical Functions Library, http://www.netlib.org/cephes/index.html