Difference Quotient - TI 81

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