HP 39gs Master Guide

SYMB mode
Test mode
As can be seen in the screen shots right, the bottom half of the screen
shows the roots (if any), the value of the discriminant and the equation in
the form y=ax
2
+bx+c.
The key labeled
changes the ‘step size’ of the movements on the
screen. Possible values for the increment are 0.5, 1 and 2.
Pressing
SYMB on the calculator, or the screen key labeled will
change the emphasis from the graph to the equation in the right hand
half of the screen. Pressing
PLOT on the calculator, or the key labeled
will change the emphasis from the equation back to the graph.
The alternative to graphical mode is symbolic mode. In
mode the student can change the coefficients
directly and see the changes reflected in the graph.
For example, on the screen shown below, the ‘v’ coefficient is high-
lighted and can be changed using the
and keys. The size of the
changes to ‘h’ and ‘v’ is controlled by the
key, and the same
range of values is available for the values of ‘a’ as in
mode.
You can move from one coefficient to the next by using the
and
keys.
As with the
mode, the equation in y=ax
2
+bx+c form, its roots
and its discriminant are shown on the right half of the screen.
The + and - keys are disabled in
mode, since their effects are
controlled instead by the
and keys once the highlight is on the ‘a’
coefficient. The
key controls the sign of ‘a’.
The final key is labeled
. This key will present the student with a
series of graphs for which they must supply the equation. The type of graph is governed by the current setting
2
. For example, if the current setting of
=
+ was at YX v then the test graphs would also
only use the v parameter instead of a, h and v simultaneously. The setting of
of
can be changed within
the
screen using the key supplied.
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HP 39gs Specifications

General

Type	Scientific
Form factor	Pocket
Product color	Gray
Internal memory	0.256 MB

Weight and Dimensions

Weight	249 g
Dimensions (WxDxH)	187 x 94 x 31 mm