Education Technology

# Knowledge Base

## Solution 13341: Using the fInt() (Function Integral) Function on the TI-83 Family, TI-84 Plus Family, or TI-Nspire™ Handheld in TI-84 Plus Mode.

### How do I use the fInt() (Function Integral) function on my TI-83 family,TI-84 Plus family, or TI-Nspire in TI-84 Plus Mode?

The fnInt( function returns the numerical integral of an expression with regards for real numbers only. The numerical integral is based on the Gauss-Kronrod method. The numerical integral is calculated with respect to the variable, given a lower limit, upper limit and a tolerance. If the tolerance is not specified it is defaulted to 1E-5. The TI-84 Plus family or TI-Nspire in TI-84 Plus mode have a template when in MATHPRINT MODE. On the TI-83 family, TI-84 Plus family in CLASSIC mode, or TI-Nspire in TI-84 Plus mode in CLASSIC mode the proper syntax for the fnInt( function is as follows:

fnInt(expression, variable, lower, upper[,tolerance]), between lower and upper, with specified tolerance.

Reference the example provided below:

Ex. Find the function integral of A2, for the variable A, with 0 as the lower bound and 1 as the upper bound on the TI-84 Plus family or TI-Nspire in TI-84 Plus mode using the MATHPRINT mode:

1) From the main screen press [MATH] and select 9:fInt(.
2) Press [0] [→] [1] [→] [ALPHA] [A] [x²] [→] [ALPHA] [A] [ENTER].

Using the TI-83 family, TI-84 Plus family or TI-Nspire in TI-84 Plus mode using the CLASSIC mode:

1) From the main screen press [MATH] and select 9:fInt(.
2) Press [ALPHA] [A] [x2] [,] [ALPHA] [A] [,] [0] [,] [1] [)] [ENTER].

Please Note: It may be necessary to update the TI-84 Plus family calculator or TI-Nspire to have MATHPRINT available. Please click here to update the Operating System (OS). Users with TI-Nspire may click here to update the OS.

Please see the TI-83 family and TI-84 Plus family guidebooks for additional information.

Please Note: TI-Nspire users may refer to the TI-84 Plus family guidebook.