4-2 Function Graphing
Getting Started is a fast-paced introduction. Read the chapter for details.
Graph a circle of radius 10, centered on the origin in the standard viewing
window. To graph a circle, you must enter separate formulas for the upper and
lower portions of the circle. Then use ZSQUARE to adjust the display to make
the functions appear as a circle.
Make sure that your TI-80 is in FUNC mode and all
STAT PLOTS are turned off.
1. Press ( to display the Y= edit screen. Press 2 ]
c 100 | @ a d ¸ to enter the expression
Y1=‡(100–X2), which defines the top half of the
circle.
The bottom half of the circle is defined by
Y2=‡(100–X2). However, you can also define
one function in terms of another; so to define
Y2=LY1, press · 2 G (to display the Y=
variables menu) 1 (to select Y1).
2. Press * 6 to select ZSTANDARD. This is a quick
way to reset the Window variables to the standard
values. It also graphs the functions; you do not need
to press ,.
Notice that the functions appear as an ellipse in
the standard viewing window.
3. To adjust the display so each “dot” represents an
equal width and height, press *, and then 5 to
select ZSQUARE. The functions are replotted and
now appear as a circle on the display.
4. To see the ZSQUARE Window variables, press
) and notice the values for XMIN, XMAX, YMIN,
and YMAX.
5. If you want to see the graph again, press ,.
Getting Started: Graphing a Circle