Texas Instruments TI-82 Getting Started page 10

The TI-82 can graph piecewise-defined functions by using the options in the TEST menu (Figure I.22) that
is displayed by pressing 2nd TEST. Each TEST function returns the value 1 if the statement is true, and the
value 0 if the statement is false.
For example, to graph the function
2
Y= ( X,T, x + 1) ( X,T, 2nd TEST 5 0 ) + ( X,T, – 1 ) ( X,T, 2nd TEST 4 0 ) (Figure I.23). Then
change the mode to Dot graph and press GRAPH to display the graph. Figure I.24 shows this graph in a
viewing window from
Figure I.23: Piecewise-defined function
I.2.4 Graphing a Circle: Here is a useful technique for graphs that are not functions, but that can be "split"
into a top part and a bottom part, or into multiple parts. Suppose you wish to graph the circle whose equation
2 2
is x y 36. First solve for
bottom semicircle, y
Use the following keystrokes to draw the circle's graph. Enter
Y (see Figure I.25) by pressing Y= CLEAR 2nd
2
2
( 36 X,T, x ). Then press GRAPH to draw them both.
I-10
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Figure I.22: 2nd TEST menu
2
x 1,
f x
x 1,
5 to 5 in both directions.
y and get an equation for the top semicircle,
2
36 x . Then graph the two semicircles simultaneously.
x < 0
(using Dot graph) enter the following keystrokes
x ≥ 0
−5
−5
Figure I.24: Piecewise-defined graph
36 x
2
( 36 X,T, x ) ENTER CLEAR (-) 2nd
5
5
2
y 36 x , and for the
2
Y
as and 36
1
TI-82 Graphics Calculator
2
x as