Casio CFX-9850G PLUS, User'S Manual & Technical Reference

Page: 84 / 486

56
This average, which is called the central difference , is expressed as:
u u u u u
To perform a differential calculation
Example To determine the derivative at point
x
= 3 for the function
y
=
x
3 +
4
x
2 +
x
–
6, when the increase/decrease of
x
is defined
as
A A A A A
x
=
1
E
–
5
Input the function
f ( x )
.
A
K
4
(CALC)
2
(
d/dx
)
v
M d+e
vx
+
v
-g,
Input point
x
=
a
for which you want to determine the derivative.
d,
Input
A
x
, which is the increase/decrease of
x
.
b E- f)
w
• In the function
f ( x )
, only X can be used as a variable in expressions. Other
variables (A through Z,
r
,
θ
) are treated as constants, and the value currently
assigned to that variable is applied during the calculation.
• Input of
A
x
and the closing parenthesis can be omitted. If you omit
A
x
, the
calculator automatically uses a value for
A
x
that is appropriate for the deriva-
tive value you are trying to determine.
• Discontinuous points or sections with drastic fluctuation can adversely affect
precision or even cause an error.
3 - 2
Differential Calculations
1 f ( a +
A
x ) – f ( a ) f ( a ) – f ( a –
A
x )
f '( a ) =
–– –––––––––––––
+
–––––––––––––
2
A
x
A
x
f ( a +
A
x ) – f ( a –
A
x )
=
–––––––––––––––––
2
A
x