HP 39gs - Manual (Page 173)

Using mathematical functions 13-21
(The | symbol is in the CHARS menu: press CHARS .
The = sign is listed in the MATH menu under Symbolic
functions.)
Symbolic
calculations in
the Function
aplet You can perform symbolic operations in the Function
aplet’s Symbolic view. For example, to find the derivative
of a function in the Function aplet’s Symbolic view, you
define two functions and define the second function as a
derivative of the first function. You then evaluate the
second function. See “To find derivatives in the Function
aplet’s Symbolic view” on page 13-22 for an example.
Finding derivatives
The HP 39gs can perform symbolic differentiation on
some functions. There are two ways of using the HP 39gs
to find derivatives.
• You can perform differentiations in HOME by using
the formal variables, S1 to S5.
• You can perform differentiations of functions of X in
the Function aplet.
To find derivatives
in HOME To find the derivative of the function in HOME, use a
formal variable in place of X. If you use X, the
differentiation function substitutes the value that X holds,
and returns a numeric result.
For example, consider the function:
1. Enter the differentiation function onto the command
line, substituting S1 in place of X.
S1
S1
2
dx x (
2
) sin ( 2 x ( ) ) cos +
HP 39gs English.book Page 21 Wednesday, December 7, 2005 11:24 PM