Numerical Derivative

Press to access the numerical derivative option which approximates the first derivative of an expression with respect to a variable at a value.

Next, enter an expression, the variable, and a value separated by commas. For example, to find the first derivative of x3 at x = 2, enter

3 2

For f(x) = x3, f'(2) = 12.

Note: The value of the derivative is found by computing the slope of the line through the points ( value- , f(value-) ) and ( value+ , f(value+) ) for some very small number .

The value of can be changed in the tolerance editor available by pressing . It typically has a value of about 0.0001.

Though this method is less accurate than der1, it can be used to evaluate any expression, including a single nesting of itself for calculating the second derivative.