# Kelvin_bei

## Definition:

$bei = kelvin\_bei(x)$ evaluates an approximation to the Kelvin function bei x.

The function is based on several Chebyshev expansions. For large x, there is a danger of the result being totally inaccurate, as the error amplification factor grows in an essentially exponential manner; therefore the function must fail.

## Parameters:

x (input, double)
The argument x of the function.
bei (output, double)
Approximation of the Kelvin function bei x.