Texas-instruments PLUS TI-89 User Manual download pdf (Page 147)

100

101

130 Chapter 7: Parametric Graphing

07PARAM.DOC TI-89/TI-92 Plus: Parametric Graphing (English) Susan Gullord Revised: 02/23/01 10:56 AM Printed: 02/23/01 2:13 PM Page 130 of 6

Use

to set

Graph = PARAMETRIC

before you define equations or

set Window variables. The Y= Editor and the Window Editor let you

enter information for the

current

Graph

mode setting only.

To graph a parametric equation, you must define both its

and

components. If you define only one component, the equation cannot

be graphed. (However, you can use single components to generate

an automatic table as described in Chapter 13.)

Be careful when using implied multiplication with

. For example:

Enter: Instead of: Because:

cos(60) tcos(60) tcos

is interpreted as a user-defined

function called

tcos

, not as implied

multiplication.

In most cases, this refers to a nonexistent

function. So the

89 / TI

92 Plus

simply

returns the function name, not a number.

The Y= Editor maintains an independent function list for each

Graph

mode setting. For example, suppose:

FUNCTION

graphing mode, you define a set of

y(x)

functions.

You change to

PARAMETRIC

graphing mode and define a set of

and

components.

When you return to

FUNCTION

graphing mode, your

y(x)

functions

are still defined in the Y= Editor. When you return to

PARAMETRIC

graphing mode, your

and

components are still

defined.

Differences in Parametric and Function Graphing

This chapter assumes that you already know how to graph y(x)

functions as described in Chapter 6: Basic Function Graphing.

This section describes the differences that apply to parametric

equations.

Setting the

Graph Mode

Defining Parametric

Equations on the

Y= Editor

Note: When using t, be sure

implied multiplication is valid

for your situation.

Tip: You can use the Defin

command from the Home

screen (see Appendix A) to

define functions and

equations for any graphing

mode, regardless of the

current mode.

Enter x and y components

on separate lines.

You can define

xt1(t) through xt99(t) and

yt1(t) through yt99(t).

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Texas-instruments PLUS TI-89 User Manual Page 147

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