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Advanced Keyboard/ALGEBRA USING THE SHARP EL-9900
Copyright © 2002, Sharp Electronics Corporation. Permission is granted to photocopy for educational use only.
Steps for graphing a circle in rectangular mode
1. To graph the circle x
2
+ y
2
= 4, solve for y in terms of x . The result is
y =
±
4 – x
2
.
2. Press Y= CL to clear the Y1 prompt. Enter Y1 = (4 – X
2
) by pressing
2ndF 4 – X/θ/T/nx
2
ENTER and then enter Y2 =
-
(4 – X
2
) by
pressing CL
(–)
2ndF VARS A (EQVARS) ENTER A (XY) 1 (Y1).
View the graph by pressing ZOOM A (ZOOM) 7 (Dec).
Steps for graphing a circle not in standard form
1. First solve the equation for y by completing the square on the y-term and
solving for y. For example, draw the graph of the circle x
2
– 2x + y
2
+ 4y = 2
by rewriting as y = ± (6 – x
2
+ 2x) – 2.
2. Enter Y1 = (6 – x
2
+ 2x), Y2 = Y1 – 2 and Y3 =
-
Y1 – 2. “Turn off” Y1 so that
it will not graph by pressing ▲ to move the blinking cursor to the Y1
expression. Press to position the blinking cursor over the = sign, and
press ENTER so that “=” is no longer darkened.
3. To view the graph, press ZOOM 7 (Dec).
4. Adjust the screen to see the bottom part of the circle by pressing ZOOM
A (ZOOM) 4 (OUT).
CONIC SECTIONS (continued)
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