HP 39gs

The c coefficient is shown as a multiple of π in radian mode rather than as a decimal. The currently active
coefficient is highlighted and can be changed using the up/down arrow keys in increments of 0.1 for the
coefficients a, b and d.
The default increment for c is
6
π
but this can be changed using the key
labeled
to either
9
π
or
4
π
.
mode, the increments are 20
o
, 30
o
or 45
o
with 30
o
being the default.
When in
The values available for the four coefficients are restricted to a given
range and only certain values within that range. This is done to make the
aplet more efficient and faster. The range of values is shown below:
Coefficient Range
a -3 to 3 in steps of 0.1
b 0.3 to 5 in steps of 0.1
c -4
π to 4π in steps of (or whatever is set by
d -3 to 3 in steps of 0.1
6
π
)
If you go to Hewlett Packard’s website you can download a worksheet for use with your class. It takes the
student through the process of deducing the effects of each of the coefficients on the shape of the graph,
requiring them to record their answers in writing. The same worksheet can be found on the author’s site at
http://www.hphomeview.com
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