* Modified Bessel function of order one
*
* Returns modified Bessel function of order one of the
* argument.
*
* The function is defined as i1(x) = -i j1( ix ).
*
* The range is partitioned into the two intervals [0,8] and
* (8, infinity). Chebyshev polynomial expansions are employed
* in each interval.
* Modified Bessel function of order one * * Returns modified Bessel function of order one of the * argument. * * The function is defined as i1(x) = -i j1( ix ). * * The range is partitioned into the two intervals [0,8] and * (8, infinity). Chebyshev polynomial expansions are employed * in each interval.