Computing Numerical Derivatives on a TI-82
or TI-83
Goal: We want to use the numerical derivative function of the calculator.
General method: The calculator has a built-in function, nDeriv, which
computes [f(a+h)-f(a-h)]/(2h) for a small value of h. You can either accept
the default value of h or choose your own.
Step by step example: Consider f(x)=x3 – x. We will
approximate f Î(2),
- With the cursor in a desired location, enter the MATH menu, find
nDeriv( and press ENTER . (nDeriv( is item 8)
- Complete the resulting expression to nDeriv(X^3–X, X, 2) and
press ENTER.
- Read the results.
Notes:
- The general form is nDeriv(expression, variable, value).
The expression can be a formula or an equation variable such as Y1
and may contain more than one variable. The value of variable then
determines which is the independant variable.
- The value of h used can be set by placing an optional 4th argument. (e.g.
nDeriv(X^3–X, X, 2,.002 ))
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