HP 39gs, Руководство пользователя, Страница: 331 / 366

Pressing down arrow at that point moved down the tree. The default is to move to the
left-most node D. This meant that the
2
was highlighted and so when you pressed
3
it was that expression which was cubed. At that point the tree now
appears as shown right with the CAS in ‘typing/editing mode’ on node G.
Pressing up arrow three times placed the highlight successively on nodes
G, then D, then B. When
2
was pressed it squared the entire
expression defined by node B which was ‘
2
3
X
’. This necessitated
brackets and so they were automatically added.
The result was the tree shown to the right, with nodes P and Q
added below node A. You may notice that it is heavily canted to
the left and this tends to be fairly typical of the way we generally
write expressions.
Now press up arrow three times and then divide by
5
.
The three up arrows moved the highlight up to node A, high­
lighting the entire expression. Dividing by 5 therefore applies to
the entire expression, with the result shown below.
+
81 *
^ X
A
B
E
C
D
2 3
F
G
+
81
*
^ X
A
B
E
C
D
2 3
G
Q
P
5
R
^
2
+
81
*
^
X
A
B
E
C
D
2 3
F
G
Q
P
^
2
S
The new tree is shown below with nodes R and S added above A.
Although it is not strictly necessary for you to understand or use
this concept of a tree of operations you may find that it will
help you to follow why the highlight behaves as it does as it
F
moves around. A final example may help with the
visualization.
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