How to Use Excel's BESSELK Function

By eHow Computers Editor

Rate: (0 Ratings)

Excel's BESSELK function returns the solution to the second linearly independent modified Bessel function for a purely imaginary number. Bessel functions have a variety of real-world applications, especially in electromagnetism and heat conduction.

Flag Article

Instructions

Difficulty: Moderate

Step1

Install the Analysis ToolPak if BESSELK returns the #NAME? error value. Select the Add-Ins menu item from the Tools menu, check the box next to the Analysis ToolPak and click on the OK button to install the Analysis ToolPak.

Step2

Learn the syntax for BESSELK. It's BESSELK(x,n) where x is the value for which this modified Bessel function will be evaluated and n is the order of the Bessel function. N must be an integer greater than or equal to zero and will be truncated to an integer if necessary.

Step3

Interpret the error values returned by BESSELK. A return error value of #VALUE! means that one of the arguments is nonnumeric. BESSELK will return the #NUM! error value if n < 0.

Step4

Look at how this nth order BESSEL function is evaluated for purely imaginary numbers. It's: K(x)= pi/2i^(n+1)[J(ix)+iY(ix] where K(x) is the nth ordered solution at x, i is the square root of -1, J(ix) and Y(ix) are the unmodified J and Y Bessel functions for ix of order n, respectively.

Step5

Study this example of BESSELK: =BESSELK(2,1) will return 0.139866. This is the value of the first order modified Bessel function of the second kind for 1.5i. Note that this modified Bessel function is actually evaluated for xi and not x.