Finding Numerical Derivatives
While the TI84+ calculators are not symbolic
manipulators (they cannot tell you the algebraic expression for a
derivative), they can tell you an approximate numerical value for a
derivative at a specific location. Several methods may be used.
Method 1:
using nDeriv(expression,
variable, value, []) 
The nDeriv command uses the symmetric difference quotient method, which
approximates the numerical derivative value as the slope of the secant
line, f ' (x) = ( f (x + )
 f (x  ))
/ 2.
As becomes smaller, the answer becomes more accurate.
Be careful!!! The use
of this method can yield an incorrect answer at nondifferentiable
points.
The default value for is
1 E 3. EXAMPLE: Find the numerical
value of the derivative for the function stated below at the indicated
location (express answer to three decimal places).
