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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–X
2
)
, which defines the top half of the
circle.
The bottom half of the circle is defined by
Y2=
‡
(100–X
2
)
. However, you can also define
one function in terms of another; so to define
Y2=
L
Y1
, 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