Casio CFX-9850G PLUS User manual

Conic Section Graphs

You can graph any one of the following types of conic sections

using the calculator’s built-in functions.

•Parabolic graph

•Circle graph

•Elliptical graph

•Hyperbolic graph

14-1 Before Graphing a Conic Section

14-2 Graphing a Conic Section

14-3 Conic Section Graph Analysis

Chapter

194

14-1 Before Graphing a Conic Section

kEntering the CONICS Mode

1. In the Main Menu, select the CONICS icon and enter the CONICS Mode.

When you do, the following built in function menu appears on the screen.

2. Use fand cto highlight the built-in function you want, and then press w.

The following nine functions are built in.

Graph Type Function

Parabola X = A (Y – K)2+ H

X = AY2+ BY + C

Y = A (X – H)2+ K

Y = AX2+ BX + C

Circle (X – H)2+ (Y – K)2= R2

AX2+ AY2+ BX + CY + D = 0

Ellipse (X – H)2(Y – K)2

–––––––– + –––––––– = 1

A2B2

Hyperbola (X – H)2(Y – K)2

–––––––– – –––––––– = 1

A2B2

(Y – K)2(X – H)2

–––––––– – –––––––– = 1

A2B2

195

14-2 Graphing a Conic Section

Example 1 To graph the circle (X – 1)2+ (Y – 1)2= 22

Use the following View Window parameters.

Xmin = –6.3 Ymin = –3.1

Xmax = 6.3 Ymax = 3.1

Xscale = 1 Yscale = 1

1. Select the function whose graph you want to draw.

cccc

2. Press wand the variable input screen appears.

•The values that appear are the values currently assigned to each variable,

which are general variables used by the calculator. If the values include an

imaginary part, only the real part appears on the display.

3. Assign values to each variable.

bwbwcw

•You can also use fand cto highlight a variable and then input a value.

4. Press 6(DRAW) to draw the graph.

•Certain View Window parameters can make a circle graph come out looking

like an ellipse. When this happens, you can use the graph correction function

(SQR) to make corrections and produce a perfect circle.

Graph function

Function variables

P. 136

196

14 - 2 Graphing a Conic Section

(X – 3)2(Y – 1)2

Example 2 To graph the hyperbola –––––––––– – –––––––––– = 1

2222

Use the following View Window parameters.

Xmin = –8 Ymin = –10

Xmax = 12 Ymax = 10

Xscale = 1 Yscale = 1

1. Select the function whose graph you want to draw.

ccccccc

2. Press wand the variable input screen appears.

3. Assign values to each variable.

cwcwdwbw

4. Press 6(DRAW) to draw the graph.

kConic Section Graphing Precautions

•Assigning the following types of values to variables contained in built-in

function produces an error.

(1) Parabola graph

A = 0

(2) Circle graph

R = 0 for (X – H)2+ (Y – K)2= R2

A = 0 for AX2+ AY2+ BX + CY + D = 0

(3) Ellipse/hyperbola graph

A = 0 or B = 0

197

Graphing a Conic Section 14 - 2

•Conic section graphs can be drawn in blue only.

•You cannot overwrite conic section graphs.

•The calculator automatically clears the screen before drawing a new conic

section graph.

•You can use trace, scroll, zoom, or sketch after graphing a conic section.

However, a conic section graph cannot be scrolled while using trace.

•You cannot incorporate graphing of a conic section into a program.

-intercept A’

-intercept A

-intercept B’

-intercept B

Focus F’ Focus F

Vertex A

Directrix

Axis of symmetry

Focus F (p, 0)

•Aparabola is the locus of points equidistant from fixed line land fixed point F

not on the line. Fixed point F is the “focus,” fixed line lis the “directrix,” the

horizontal line that passes through the focus directrix is the “axis of symme-

try,” the length of a straight line that intersects the parabola, passes through

the locus, and is parallel to fixed line lis the “latus rectum,” and point A where

the parabola intersects the axis of symmetry is the “vertex.”

•An ellipse is the locus of points the sum of the distances of each of which

from two fixed points F and F’ is constant. Points F and F’ are the “foci,”

points A, A’, B, and B’ where the ellipse intersects the x- and y-axes are the

“vertexes,” the x-coordinate values of vertexes A and A’ are called

x-intercepts, and the y-coordinate values of vertexes B and B’ are called

y-intercepts.

Latus rectum

CFX

198

•Ahyperbola is the locus of points related to two given points F and F’ such

that the difference in distances of each point from the two given points is

constant.

Points F and F’ are the “foci,” points A and A’ where the hyperbola intersects

the x-axis are the “vertexes,” the x-coordinate values of vertexes A and A’ are

called x-intercepts, the y-coordinate values of vertexes A and A’ are called y-

intercepts, and straight lines land l' , which get closer to the hyperbola as

they move away from the foci are “asymptotes.”

14 - 2 Graphing a Conic Section

Vertex

A’

Vertex

Focus F' Focus F

Asymptote

199

14-3 Conic Section Graph Analysis

You can determine approximations of the following analytical results using conic

section graphs.

•Focus/vertex calculation

•Latus rectum calculation

•Center/radius calculation

•x-/y-intercept calculation

•Directrix/axis of symmetry drawing and analysis

•Asymptote drawing and analysis

After graphing a conic section, press 5(G-Solv) to display the Graph Analysis

Menu.

Parabolic Graph Analysis

•{FOCS} ... {determines the focus}

•{SYM}/{DIR} ... draws the {axis of symmetry}/{directrix}

•{VTX}/{LEN} ... determines the {vertex}/{latus rectum}

Circle Graph Analysis

•{CNTR}/{RADS} ... determines the {center}/{radius}

Ellipse Graph Analysis

•{FOCS}/{X-IN}/{Y-IN} ... determines the {focus}/{x-intercept}/{y-intercept}

Hyperbolic Graph Analysis

•{FOCS}/{X-IN}/{Y-IN}/{VTX} ... determines the {focus}/{x-intercept}/{y-intercept}/

{vertex}

•{ASYM} ... {draws the asymptote}

The following examples show how to use the above menus with various types of

conic section graphs.

uTo calculate the focus and vertex [G-Solv]-[FOCS]/[VTX]

Example To determine the focus and vertex for the parabola

X = (Y – 2)2+ 3

Use the following View Window parameters.

Xmin = –1 Ymin = –5

Xmax = 10 Ymax = 5

Xscale = 1 Yscale = 1

200

5(G-Solv)

1(FOCS)

(Calculates the focus.)

5(G-Solv)

4(VTX)

(Calculates the vertex.)

•When calculating two foci for an ellipse or hyperbolic graph, press eto

calculate the second focus. Pressing dreturns to the first focus.

•When calculating two vertexes for a hyperbolic graph, press eto calculate

the second vertex. Pressing dreturns to the first vertex.

uTo calculate the latus rectum [G-Solv]-[LEN]

Example To determine the latus rectum for the parabola X = (Y – 2)2+ 3

Use the following View Window parameters.

Xmin = –1 Ymin = –5

Xmax = 10 Ymax = 5

Xscale = 1 Yscale = 1

5(G-Solv)

5(LEN)

(Calculates the latus rectum.)

uTo calculate the center and radius [G-Solv]-[CNTR]/[RADS]

Example To determine the center and radius for the circle

X2+ Y2– 2X – 2Y – 3 = 0

Use the following View Window parameters.

Xmin = –6.3 Ymin = –3.1

Xmax = 6.3 Ymax = 3.1

Xscale = 1 Yscale = 1

14 - 3 Conic Section Graph Analysis

201

5(G-Solv)

1(CNTR)

(Calculates the center.)

5(G-Solv)

2(RADS)

(Calculates the radius.)

uTo calculate the x- and y-intercepts [G-Solv]-[X-IN]/[Y-IN]

Example To determine the x- and y-intercepts for the hyperbola

(X – 1)2(Y – 1)2

–––––––––– – –––––––––– = 1

2222

Use the following View Window parameters.

Xmin = –6.3 Ymin = –3.1

Xmax = 6.3 Ymax = 3.1

Xscale = 1 Yscale = 1

5(G-Solv)

2(X-IN)

(Calculates the x-intercept.)

5(G-Solv)

3(Y-IN)

(Calculates the y-intercept.)

•Press eto calculate the second set of x-/y-intercepts. Pressing dreturns to

the first set of intercepts.

Conic Section Graph Analysis 14 - 3

202

uTo draw and analyze the axis of symmetry and directrix

[G-Solv]-[SYM]/[DIR]

Example To draw the axis of symmetry and directrix for the parabola

X = 2(Y – 1)2+ 1

Use the following View Window parameters.

Xmin = –6.3 Ymin = –3.1

Xmax = 6.3 Ymax = 3.1

Xscale = 1 Yscale = 1

5(G-Solv)

2(SYM)

(Draws the axis of symmetry.)

5(G-Solv)

3(DIR)

(Draws the directrix.)

uTo draw and analyze the asymptotes [G-Solv]-[ASYM]

Example To draw the asymptotes for the hyperbola

(X – 1)2(Y – 1)2

–––––––––– – –––––––––– = 1

2222

Use the following View Window parameters.

Xmin = –6.3 Ymin = –5

Xmax = 6.3 Ymax = 5

Xscale = 1 Yscale = 1

5(G-Solv)

5(ASYM)

(Draws the asymptotes.)

14 - 3 Conic Section Graph Analysis

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