HP 40gs HP 39gs_40gs_Mastering The Graphing Calculator_English_E_F2224-90010.p - Page 98
The Polar Aplet, Choose XRng, YRng & Rng, Step and smoothness, Changing the default for Step
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13 THE POLAR APLET 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(3θ ) R2(θ ) = 0.5θ R3(θ ) = 3 + 2sin(10θ ) Choose XRng, YRng & θRng 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. θStep and smoothness 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 ≤ 2π and the default value for θStep is π/24. Changing the default for θStep 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 try π/60. Circular circles 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