# The Excel BESSELI Function

## Function Description

The Excel Besseli function calculates the modified Bessel functions, In(x), (also known as the hyperbolic Bessel Functions). These functions are the equivalent of the Bessel functions, evaluated for purely imaginary arguments.

The syntax of the Besseli function is:

BESSELI( x, n )

where the function arguments are:

 x - The value at which the function is to be evaluated. n - A positive integer, representing the order of the function.(If the supplied value of n is a decimal, this is truncated to an integer by Excel).

## Besseli Function Example

Order 1, 2 & 3 Modified Bessel Functions In(x)

The above chart on the right shows the order 1, 2 and 3 modified Bessel functions, In(x).

If you want to calculate the value of the order 1 modified Bessel function at x = 4.5, this can be done using the Excel Besseli function, as follows:

=BESSELI( 4.5, 1 )

which gives the result 15.38922293.

See the Microsoft Office website for further details on the Excel Besseli function.

## Besseli Function Errors

If you get an error from the Excel Besseli function this is likely to be one of the following:

Common Errors
 #NUM! - Occurs if the supplied value of n is < 0. #VALUE! - Occurs if any of the supplied arguments are non-numeric.