Texas Instruments -84 Plus, Manual Book

Page: 63 / 696

Chapter 2: Math, Angle, and Test Operations 60
nDeriv( nDeriv( nDeriv( nDeriv(
nDeriv(
(numerical derivative) returns an approximate derivative of
expression
with respect
to
variable
, given the
value
at which to calculate the derivative and
H
(if not specified, the
default is 1
â
L
3).
nDeriv(
is valid only for real numbers.
nDeriv( expression , variable , value
[
,
H
]
)
nDeriv(
uses the symmetric difference quotient method, which approximates the
numerical derivative value as the slope of the secant line through these points.
As
H
becomes smaller, the approximation usually becomes more accurate.
You can use
nDeriv(
once in
expression
. Because of the method used to calculate
nDeriv(
,
the TI-84 Plus can return a false derivative value at a nondifferentiable point.
f
′
x
( )
f x
ε
+
( )
f x
ε
–
( )
–
2
ε
------------------------------------------ =