Storing And Retrieving Memories - HP 39gs Master Manual

S t o r i n g a n d R e t
S t o r i n g a n d R e t
Each of the alphabetic characters shown in orange below the keys can function as a memory. Some
examples of this are shown in the third of the four examples above where the values of
stored into , and
A B C
key, which is one of the screen keys listed at the bottom of the
obtaining even more memories than these 26 alphabetic ones, such as storing values into a list (see page
215), but 26 is enough for most purposes.
Once stored into memory, values can be used in calculations by typing
the letter in place of the value. Typing a letter and pressing
display memory's contents. See right.
There is an advantage to storing results in memories, particularly if they
are long decimals, or if you're going to be re-using the result a number
of times.
As an example, we will perform the calculation of
We will do this in two stages, calculating the top and bottom of the
fraction and storing the results in memories.
Firstly the top of the fraction, storing the result in memory
bottom, storing in , and then finally the result...
B
As another example, suppose we were evaluating 3 x x
value x = −3 . We can store -3 into the memory X and then use that
symbol in the calculation as shown right. The advantage of this is that if
we now wanted to evaluate that expression for other values then we
need only store a different value into X and then
for re-evaluation. Clearly, if the expression is complex, this can be very
helpful.
Calculator Tip
1. The memory
2. A common error is to forget to put brackets around negatives when
r i e v i n g M e m o r i
r i e v i n g M e m o r i
prior to the use of the quadratic formula. All of this storing of values is done with the
is the exception to the above information. It is used
X
to store the current cursor position in the
access it in other places. Values stored in
next time you use the
evaluating expressions with powers. For example, evaluating
2
x − as -3 – 1 rather than as (-3)
2
1
storing the value into memory X and evaluating X
particularly useful in very complex expressions. Any memory can
be used in this way, not just
e s
e s
HOME
will
ENTER
× −
4 ( 3)
2 +
5
.
⋅ −
2 3 5
, then the
A
+ 7 for the
−
2
the expression
PLOT
X
view.
PLOT
2
– 1. This can be avoided by
.
X
39
, and
1 -3
view. There are ways of
view so that you can
will be overwritten the
2
-1. This is
are
-4