HP 39gs Graphing manual Finding derivatives, To find derivatives in Home

Symbolic calculations in the Function aplet

(The symbol is in the CHARS menu: press CHARS. The = sign is listed in the MATH menu under Symbolic functions.)

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:

dx( sin (x 2 ) + 2 cos (x) )

1.Enter the differentiation function onto the command line, substituting S1 in place of X.

S1

S1

2

Using mathematical functions 13-21