k1

Modified Bessel function, third kind, order one.

SYNOPSIS:

double x, y, k1();
y = k1(x);

DESCRIPTION:

Computes the modified Bessel function of the third kind, of order one of the argument.
The range is partitioned into the two intervals [0,2] and (2, infinity). Chebyshev polynomial expansions are employed in each interval.

ACCURACY:
                      Relative error:
arithmetic   domain     # trials      peak         rms
    DEC       0, 30        3300       8.9e-17     2.2e-17
    IEEE      0, 30       30000       1.2e-15     1.6e-16

ERROR MESSAGES:

   message       condition      value returned
   domain          x <= 0          MAXNUM