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1 Definite Integrals

1 Definite Integrals on the Home Screen

The TI-83/84 computes a definite integral using the fnint( ) function. To access the function, press the [MATH] button and then scroll up or down to find 9:fnint(.

Example: Suppose you must find the definite integral [pic]. By symmetry, that’s [pic], which evaluates to –2(cos π/4 – cos 0) = –2(√(2)/2 – 1) = 2–√(2), approximately 0.5858.

Here’s how to check this on the TI-83/84:

|On the home screen, select fnint. |[MATH] [9] |

|First argument: the integrand |sin x| |[MATH] NUM [1] for abs( |

| |[sin] [[x,T,θ,n]] [)] for sin(x) |

| |[)] for the closing parenthesis for abs( |

|Second argument: the variable of integration x |[,] [x,T,θ,n] |

|Third argument: the lower limit –π/4 |[,] [(-)] [2nd ^ makes π] [÷] 4 |

|Fourth argument: the upper limit π/4 |[,] [2nd ^ makes π] [÷] 4 |

|The optional fifth argument, tolerance, is generally not needed. |[)] [ENTER] |

| |  |

| |[pic] |

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