Differentiating - HP 39g Master Manual

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:
∂
,
X function ( )
where function is defined in terms of X.
The function can either be already defined in the SYMB view of the Function
aplet, or entered into the brackets as above.
The ∂ symbol most easily obtained by pressing the key labeled d/dx.
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.
The reason for this is that the result you see is
−
the derivative of evaluated at whatever
2
x x
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
x −
the value of the derivative 2 at the value of x = 2.
1
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.
(..or S2 to S5) The drawback of this is simply
the awkwardness of having to work with S1's
rather than with X's.
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