hp40g+.book Page 16 Friday, December 9, 2005 1:03 AM
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DERIV
DERVX
14-16
Derivative and partial derivative
DERIV has two arguments: an expression (or a function)
and a variable.
DERIV returns the derivative of the expression (or the
function) with respect to the variable given as the second
parameter (used for calculating partial derivatives).
Example
Calculate:
2
3
∂ x y
(
⋅
⋅
x y ⋅
)
z
+
--------------------------------------------- -
∂z
Typing:
2
3
DERIV(X·Y
·Z
+ X·Y,Z)
gives:
2
2
⋅ ⋅
⋅
3 x y
z
Derivative
DERVX has one argument: an expression. DERVX
calculates the derivative of the expression with respect to
the variable stored in VX.
For example, given:
x
x
⎛
f x ( )
------------- -
----------- -
=
+
ln
⎝
x 1
2
x
–
1
calculate the derivative of f.
Type:
X
⎛
⎛
-------------- -
DERVX
+
LN
⎝
⎝
2
X
–
1
Or, if you have stored the definition of f(x) in F, that is, if
you have typed:
X
⎛
⎛
-------------- -
TORE
+
LN
⎝
⎝
2
X
–
1
then type:
+
1
⎞
⎠
–
X
+
1
⎞
⎞
------------ -
⎠
⎠
X 1
–
X
+
1
⎞ F ,
⎞
------------ -
⎠
⎠
X 1
–
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