HP 39gs_40gs_Mastering The Graphing Calculator_English_E_F2224-90010

Differentiating

There are different approaches that can be taken to differentiating, most

of which are best done in the

SYMB view of the Function aplet.

The syntax of the differentiation function is:

∂

( function )

where function is defined in terms of X.

The function can be already defined in the

SYMB view of the Function aplet as shown in functions F1(X) and

F2(X) in the screen shot above. Alternatively it can be directly entered into the brackets as shown in function

F3(X).

The

∂ symbol most easily obtained by pressing the key

labeled

. It can also be found in the MATH menu.

One point to remember is that if you use this function in the

HOME view

you may not receive the result you expect. If you try this yourself your

result will probably not be the same as that shown right.

The reason for this is that the result you see is the derivative of

−

evaluated at whatever value of x happens to be currently in memory.

This can be seen more clearly if we store a specific value into the

memory

X beforehand. In the example shown right, the answer of 3 is

the value of the derivative

2x −1 at the value of x = 2.

But what of algebraic differentiation? It is possible but not very

convenient to do this in the

HOME view using a “formal variable” of

S1. The drawback of this is simply the awkwardness of having to work

with

S1’s rather than with X’s.