Exact Values on a Graph
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TI-Nspire
CAS
How To
Teacher
15min
It is often desirable to display exact values on a graph. The Graph application is primarily a numerical
environment, however it is possible to change the x and y axis scale to display exact values such as radians
(multiples of π) or determine the exact value of a point on the graph.
Syntax:
Exact values in the Graph application are achieved by editing the text directly.
Functionality:
Exact values can be applied to the axis scale, end points and for points on a graph. Exact
values remain when the graph display is changed can not currently be initiated through the
Window Settings dialog box.
Examples:
(1)
Display the x axis scale for a trigonometric function as multiples of π
(2)
Display exact value for y given a specific x value
Example 1 – Display exact values on the x axis scale
Start a new TI-Nspire Graphs application and graph the
function:
f1(x) = sin(x)
Use the mouse to navigate to the x axis scale, the word ‘text’ is
displayed.
Click on the axis scale once to highlight the value.

When several objects are located in close proximity use
the [Tab] key to navigate between these objects. The
current object is identified through the corresponding
text.
(c) Texas Instruments 2011, Author: Peter Fox
how to exact values on a graph
Click on the value a second time to edit.
Backspace over the value and change it to:
π/2
Press [enter] to accept the new axis scale.
Repeat this process to change the maximum and minimum
values displayed on the x axis.
Start by clicking on the maximum value displayed on the x axis
and change the value to:
2π

Instead of using the [enter] key to accept changes, use
the [tab] key to automatically skip to the next axis
setting.
Change the following:
•
•
•
Min x = -2 π
Min y = -2
Max y = 2
Questions
1.
What happens if you type 2pi instead of using the symbol for π?
2.
Insert a calculator page and store the value of π in a. Example: a := π. Return to the Graphs page and
try using a instead of π. What happens?
3.
-1
In some courses graphs of f(x)=sin (x) are required. In these cases it is very powerful to show the
exact values on the y axis in multiples of π. Graph f(x)=sin-1(x) and set the following axis
measurements:
•
•
•
•
•
•
Max value x = 2
Min value x = -2
X – scale = 1/4
Max value y = π
Min value y = -π
Y – Scale = π/4
(c) Texas Instruments 2011, Author: Peter Fox
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how to exact values on a graph
Example 2 – Display exact value for y given a specific x value
Start a new TI-Nspire Graphs application and graph the
function:
x
f1(x) = e
Use the [menu] to access Points & Lines and choose Point On.
Use the mouse to navigate to the graph and click once to
select the graph and then again to place a point on the graph.
Once the point is displayed on the graph press [esc] to release
the Point On tool.
Click the mouse once on the x coordinate of the point to select
the value. Click again to edit the value.
(c) Texas Instruments 2011, Author: Peter Fox
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how to exact values on a graph
Back space over the x value and type in a value of:
–2
Press [enter] to accept the change and notice what happens to
the corresponding y value.

An x value of 2 can be entered; however the point will
disappear from the standard window settings.
To have the coordinates displayed on the screen drag
them away from the actual point so that they do not
move when the point is moved.
Questions
1.
On the computer software what happens if x = ½ compared with x = 0.5?
2.
Change the function so that f ( x ) = ln( x ) , does the point remain on the graph?
3.
With f ( x ) = ln( x ) change the x value to something outside the domain, such as x = -1, what
happens?
(c) Texas Instruments 2011, Author: Peter Fox
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