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 y = 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 .