3.5.1.3.17 Bessel_k1

Definition:

\(K1 = bessel\_k1(x)\) evaluates an approximation to the modified Bessel function of the second kind,\(K_1\left( x\right) \) . The function is based on Chebyshev expansions.

For more information please review the s18adc function in the NAG document.

Parameters:

x (input, double)

The argument x of the function. Constraint: x> 0.0.

i1 (output, double)

Approximation of the modified Bessel function of the second kind.