Chapter 8: Polar Graphing 137
08POLAR.DOC TI-89/TI-92 Plus: Polar Graphing (English) Susan Gullord Revised: 02/23/01 10:57 AM Printed: 02/23/01 2:14 PM Page 137 of 6
The Window Editor maintains an independent set of Window
variables for each Graph mode setting (just as the Y= Editor
maintains independent function lists). Polar graphs use the following
Window variables.
Variable Description
qmin, qmax Smallest and largest q values to evaluate.
qstep Increment for the q value. Polar equations are
evaluated at:
r(qmin)
r(qmin+qstep)
r(qmin+2(qstep))
... not to exceed ...
r(qmax)
xmin, xmax,
ymin, ymax
Boundaries of the viewing window.
xscl, yscl Distance between tick marks on the x and y axes.
Standard values (set when you select 6:ZoomStd from the „ Zoom
toolbar menu) are:
qmin = 0. xmin = ë10. ymin = ë10.
qmax = 2p(6.2831853... radians
or 360 degrees) xmax = 10. ymax = 10.
qstep = p/24 (.1308996... radians
or 7.5 degrees) xscl = 1. yscl = 1.
You may need to change the standard values for the q variables
(qmin, qmax, qstep) to ensure that enough points are plotted.
To display coordinates as r and q values, use:
ƒ 9
— or —
TI-89: ¥Í
TI-92 Plus: ¥F
to set Coordinates = POLAR. If Coordinates = RECT, the polar
equations will be graphed properly, but coordinates will be displayed
as x and y.
When you trace a polar equation, the q coordinate is shown even if
Coordinates = RECT.
Window Variables
Note: You can use a
negative qstep. If so, qmin
must be greater than qmax.
Setting the Graph
Format