Texas Instruments TI-92 Owners Manual - Page 188

Implicit Plots, Explicit and Implicit Forms, Selecting the Graph Format Style, Forms

Page 188 highlights

Implicit Plots An implicit plot is used primarily as a way to graph 2D implicit forms that cannot be graphed in function graphing mode. Technically, an implicit plot is a 3D contour plot with a single contour drawn for z=0 only. Explicit and Implicit Forms Tip: You can also graph many implicit forms if you either: • Express them as parametric equations. Refer to Chapter 7. • Break them into separate, explicit functions. Refer to the preview example in Chapter 6. In 2D function graphing mode, equations have an explicit form y=f(x), where y is unique for each value of x. Many equations, however, have an implicit form f(x,y)=g(x,y), where you cannot explicitly solve for y in terms of x or for x in terms of y. y is not unique for each x, so you cannot graph this in function graphing mode. By using implicit plots in 3D graphing mode, you can graph these implicit forms without solving for y or x. Rearrange the implicit form as an equation set to zero. f(x,y)ì g(x,y)=0 In the Y= Editor, enter the nonzero side of the equation. This is valid because an implicit plot automatically sets the equation equal to zero. z1(x,y)=f(x,y)ì g(x,y) For example, given the ellipse equation shown to the right, enter the implicit form in the Y= Editor. If xñ +.5yñ =30, then z1(x,y)=xñ +.5yñ ì 30. Selecting the Graph Format Style Note: From the Graph screen, you can switch to the other graph format styles by pressing: TI-89: Í TI-92 Plus: F However, to return to IMPLICIT PLOT press: TI-89: ¥ Í TI-92 Plus: ¥ F In 3D graphing mode, define an appropriate equation and graph it as you would any 3D equation, with the following exception. Display the GRAPH FORMATS dialog box from the Y= Editor, Window editor, or Graph screen. TI-89: ¥ Í TI-92 Plus: ¥ F Then set: Style = IMPLICIT PLOT Chapter 10: 3D Graphing 171

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Chapter 10: 3D Graphing
171
In 2D function graphing mode,
equations have an explicit form
y=f(x), where y is unique for
each value of x.
Many equations, however, have
an implicit form f(x,y)=g(x,y),
where you cannot explicitly
solve for y in terms of x or for x
in terms of y.
By using implicit plots in 3D graphing mode, you can graph these
implicit forms without solving for y or x.
Rearrange the implicit form as
an equation set to zero.
f(x,y)
ì
g(x,y)=0
In the Y= Editor, enter the non-
zero side of the equation. This
is valid because an implicit plot
automatically sets the equation
equal to zero.
z1(x,y)=f(x,y)
ì
g(x,y)
For example, given the ellipse
equation shown to the right,
enter the implicit form in the
Y= Editor.
If
x
ñ
+.5y
ñ
=30,
then
z1(x,y)=x
ñ
+.5y
ñì
30.
In 3D graphing mode, define an appropriate equation and graph it as
you would any 3D equation, with the following exception. Display
the
GRAPH FORMATS
dialog box from the Y= Editor, Window editor,
or Graph screen.
TI
-
89:
¥Í
TI
-
92 Plus
:
¥
F
Then set:
Style = IMPLICIT PLOT
Implicit Plots
An implicit plot is used primarily as a way to graph 2D implicit
forms that cannot be graphed in function graphing mode.
Technically, an implicit plot is a 3D contour plot with a single
contour drawn for z=0 only.
Explicit and Implicit
Forms
Tip:
You can also graph
many implicit forms if you
either:
Express them as
parametric equations.
Refer to Chapter 7.
Break them into
separate, explicit
functions. Refer to the
preview example in
Chapter 6.
Selecting the Graph
Format Style
Note:
From the Graph
screen, you can switch to
the other graph format
styles by pressing:
TI
-
89
:
Í
TI
-
92 Plus:
F
However, to return to
IMPLICIT PLOT
press:
TI
-
89
:
¥Í
TI
-
92 Plus
:
¥
F
y is not unique for each x, so
you cannot graph this in
function graphing mode.