HP 39gs Master Guide

Choose XRng, YRng &
θ Rng
θ Step and smoothness
Changing the default for
θ Step
Circular circles
13
T
T
H
H
E
E
P
P
O
O
L
L
A
A
R
R
A
A
P
P
L
L
E
E
T
T
This aplet is used to graph functions of the type where the radius r is a function of the angle
θ (theta). As with
the Parametric aplet, it is very similar to the Function aplet and so the space devoted to it here is limited
mainly to the way it differs. Some examples of functions of this type, together with their graphs are:
R1(
θ
) = 4 cos(3 θ ) R2(
θ
)
=
0.5 θ R3(
θ
) =+3 2 sin(10 θ )
The
PLOT SETUP view shows that ranges must be specified not only for
X and Y but for θ. The values set for XRng and YRng control the length
of the axes. The movement of the cursor follows the increments set for
θ
in
θStep regardless of the resulting X and Y positions.
The values of
θRng and for θStep are critical in controlling the appearance of the graph. The values set for
θRng control how much of the graph is drawn, while the values for XRng and YRng only control how much
of the graph is displayed on the screen once drawn.
θStep controls how smooth the graph is, as did TStep
in the Parametric aplet. The default values for
θRng are 0
≤
θ
≤ 2 π and the default value for θStep is
π
/
24
.
The default for
θStep often results in graphs which are not very smooth and 0.05 is a better compromise
between smoothness & speed. If you particularly want to use a fraction of
π to aid in tracing the graph then
π
try
/
60
.
If it is important that graphs of circles do not look oval, then use the
default values for the axes. If the resulting axes don’t show enough of
the function, then
in or out. The Square option can also
be used to achieve round circles.
98

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