# Manuals/calci/BESSELI

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BESSELI(x,n)

• is the value to evaluate the function
• is an integer which is the order of the Bessel function.
• BESSELI(), returns the modified Bessel Function In(x).

## Description

• This function gives the value of the modified Bessel function.
• Bessel functions is also called Cylinder Functions because they appear in the solution to Laplace's equation in cylindrical coordinates.
• Bessel's Differential Equation is defined as:

where is the arbitrary complex number.

• But in most of the cases α is the non-negative real number.
• The solutions of this equation are called Bessel Functions of order .
• Bessel functions of the first kind, denoted as .
• The order modified Bessel function of the variable is:

, where :

• This function will give the result as error when:
1. or  is non numeric
2., because  is the order of the function.


## ZOS

• The syntax is to calculate BESSELI IN ZOS is .
• is the value to evaluate the function
• is an integer which is the order of the Bessel function.
• For e.g.,BESSELI(0.25..0.7..0.1,42)

## Examples

1. BESSELI(3,2) = 2.245212431 this is the derivative of .
2. BESSELI(5,1) = 24.33564185
3. BESSELI(6,0) = 67.23440724
4. BESSELI(-2,1) = -1.59063685
5. BESSELI(2,-1) = #N/A (ORDER OF FUNCTION < 0).

BESSEL Equation