## 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 x^{3}
at x = 2, enter

3
2

For f(x) = x^{3}, 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.