# Knowledge Base

## Solution 34694: Using the fInt() (Function Integral) Function on the TI-84 Plus C Silver Edition Graphing Calculator.

### How do I use the fInt() (Function Integral) function on my TI-84 Plus C Silver Edition graphing calculator?

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 C Silver Edition has a template when in MATHPRINT MODE. When 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.

Example: 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 C Silver Edition using the MATHPRINT mode:

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