Gradient At A Point - HP 39g Master Manual

Gradient at a point

This can be introduced via the Function aplet.
In the Function aplet, enter the function being studied into F1(X).
To examine the gradient at x=3, store 3 into
memory A in the HOME view as shown right.
Return to the SYMB view, un-CHK F1(X) and
enter the expression
F2(X)=(F1(A+X)-F1(A))/X in F2(X).
This is the basic differentiation formula with X
( )
( )
+ −
f a h f a
( )
taking the role of h and A being the point of
=
f a ' lim
→
h
h 0
evaluation.
Change to the NUM SETUP view and change
the NumType to "Build Your Own". By
entering successively smaller values for X you
can now investigate the limit as h tends
towards zero.
To investigate the gradient at a different point simply change back to the
HOME view, enter a new value into A and then return to the NUM view.
The disadvantage of the previous
method is that it is not very visual. An
alternative is to use an aplet
downloaded from the web.
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