Difference Quotient - TI 81

Introduction
This program estimates the value of a derivative at a point using the difference quotient $f^\prime(A)\approx{f(A+H)-f(A)\over H}$

If you have not used one of the programs posted on this website before, you should read through the information in the Intro to Programming section first.

The Program

:Disp "A" {Disp is in PRGM under I/O}

:Input X {Input is in PRGM under I/O}

:Disp "H"

:Input H

:Y1 $\to$ B {Y1 is in Y-VARS under FUNCTION} {The arrow is STO}

:X+H $\to$ X

:Y1 $\to$ C

:(C-B)/H $\to$ D

:Disp D

Running the Program

You will need to enter a function f(x) into Y1 before running the program. To test the program try the following:

f(x) = x³, A=2, H=0.01.

The answer should be 12.0601

:Disp "A"	{Disp is in PRGM under I/O}
:Input X	{Input is in PRGM under I/O}
:Disp "H"
:Input H
:Y1 $\to$ B	{Y1 is in Y-VARS under FUNCTION} {The arrow is STO}
:X+H $\to$ X
:Y1 $\to$ C
:(C-B)/H $\to$ D
:Disp D