beautypg.com

Texas Instruments TI-85 User Manual

Page 14

background image

B-14

TI-85/TI-86 Graphing Calculators

Copyright © Houghton Mifflin Company. All rights reserved.

Notice that you could have typed the v(t), with input
variable t, directly in the solver. The solution is, of
course, the same.

If there is more than one solution to an equation, you need to give the solver an approximate
location for each answer. Suppose you are given q(x) = 8x

2

+ 54.65x Ð 163 and asked to find

what input(s) correspond to an output of q(x) = 154. (The procedure outlined below also
applies to finding where two functions are equal.)

Enter 8x

2

+ 54.65x Ð 163 in one location, say

y

1

, and 154

in another location, say

y

2

, in the

y(x)=

list.

(Remember that if the input variable in the equation
is not x, you must rewrite the equation in terms of x to
graph using the

y(x)=

list.)

To better obtain a guess as to where

y

1

equals (intersects)

y

2

, graph the equations.

If you are not told where you want to view the graph,

begin by pressing

GRAPH

F3

(

ZOOM

)

F4

(

ZSTD

) or

GRAPH

F3

(

ZOOM

)

MORE

F4

(

ZDECM

) .

You want to see a ÒgoodÓ graph, that is, one that shows
all the important features. In this case, the important
features are where

y

1

and

y

2

intersect.

Neither this graph nor the previous one is a good graph
for viewing the intersections.

To improve the view, use

EXIT

F2

(

RANGE

or

WIND

) * and

change to

xMin =

15

,

xMax = 8

,

yMin =

300

, and

yMax = 400

. Draw the graph with

F3

(

GRAPH

) .

(There are many other windows that work just as well
as the one shown to the right. Also, instead of setting
a window manually, you could draw the graph with

ZFIT

in the

ZOOM

menu

.)

*The current settings for the graphics screen are obtained with

GRAPH

F2

(

RANGE

) on the

TI-85 and with

GRAPH

F2

(

WIND

) on the TI-86. When the screen appears, the word

RANGE

is at the top of the TI-85 screen and the word

WINDOW

is at the top of the TI-86

screen. Because the only difference in the calculators in this situation is the name that is
used, we from this point forward refer to this key for both calculators as

F2

(

RANGE

or

WIND

) . In such cases, the screen shown in the right column will be the one

from the TI-85.