Math, Angle, and Test Operations 2-9
NDERIV(
(numerical derivative,
MATH MATH
, item 6) returns
an approximate derivative of an expression with respect to a
specified variable, given the value at which to calculate the
derivative, and
H
(optional; if none is specified, 1
í
-
3 is used).
NDERIV(
expression
,
variable
,
value
)
or
NDERIV(
expression
,
variable
,
value
,
H
)
NDERIV(
uses the symmetric difference quotient method (as
shown in the formula below), which approximates the
numerical derivative value as the slope of the secant line
through the points:
f(
X
+
H
)–f(
X
–
H
)
f
¢
(
x
) =
2
H
As
H
gets smaller, the approximation usually gets more
accurate.
Because of the method used,
NDERIV(
can return a false
derivative value at a nondifferentiable point.
NDERIV(
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