Texas Instruments TI-89 Titanium User Manual page 394

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.
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.
For example, given the ellipse equation
shown to the right, enter the implicit form
in the Y= Editor.
You can also graph many implicit forms if you either:
Notes:
• Express them as parametric equations.
• Break them into separate, explicit functions.
Selecting the Graph Format Style
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:
8 Í
3D Graphing
f(x,y)–g(x,y)=0
z1(x,y)=f(x,y)–g(x,y)
2 2
If x +.5y =30,
2
then z1(x,y)=x +.5y
2
–30.
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