Texas Instruments TI-80 Manual

$TITLEPG.DOC TI-80, ENG, 135x205mm Bob Fedorisko Revised: 02/15/01 10:36 AM Printed: 02/15/01 10:38
AM Page 1 of 2
TI-80
GRAPHING CALCULATOR
GUIDEBOOK
TI-GRAPH LINK, Calculator-Based Laboratory, CBL, CBL 2, Calculator-Based Ranger, CBR,
Constant Memory, Automatic Power Down, APD, and EOS are trademarks of Texas
Instruments Incorporated.
Windows is a registered trademark of Microsoft Corporation.
Macintosh is a registered trademark of Apple Computer, Inc.
© 1995–1997, 2001 by Texas Instruments Incorporated.

$TITLEPG.DOC TI-80, ENG, 135x205mm Bob Fedorisko Revised: 02/15/01 10:36 AM Printed: 02/15/01 10:38
AM Page 2 of 2
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implied, including but not limited to any implied warranties of
merchantability and fitness for a particular purpose, regarding any
programs or book materials and makes such materials available
solely on an “as-is” basis.
In no event shall Texas Instruments be liable to anyone for
special, collateral, incidental, or consequential damages in
connection with or arising out of the purchase or use of these
materials, and the sole and exclusive liability of Texas
Instruments, regardless of the form of action, shall not exceed the
purchase price of this calculator. Moreover, Texas Instruments
shall not be liable for any claim of any kind whatsoever against
the use of these materials by any other party.
This equipment has been tested and found to comply with the
limits for a Class B digital device, pursuant to Part 15 of the FCC
rules. These limits are designed to provide reasonable protection
against harmful interference in a residential installation. This
equipment generates, uses, and can radiate radio frequency
energy and, if not installed and used in accordance with the
instructions, may cause harmful interference with radio
communications. However, there is no guarantee that interference
will not occur in a particular installation.
If this equipment does cause harmful interference to radio or
television reception, which can be determined by turning the
equipment off and on, you can try to correct the interference by
one or more of the following measures:
• Reorient or relocate the receiving antenna.
• Increase the separation between the equipment and receiver.
• Connect the equipment into an outlet on a circuit different
from that to which the receiver is connected.
• Consult the dealer or an experienced radio/television
technician for help.
Caution: Any changes or modifications to this equipment not
expressly approved by Texas Instruments may void your authority
to operate the equipment.
Important
US FCC
Information
Concerning
Radio Frequency
Interference

Introduction iii
This manual describes how to use the TI.80 Graphing Calculator. Getting Started
gives a quick overview of its features. The first chapter gives general
instructions on operating the TI.80. Other chapters describe its interactive
features. The applications in Chapter 11 show how to use these features
together.
Using this Guidebook Effectively.................... viii
Glossary ......................................... xii
TI-80 Keyboard ................................... 2
First Steps ....................................... 3
TI-80 Menus...................................... 4
Entering a Calculation: Compound Interest ........... 5
Continuing a Calculation ........................... 6
Defining a Function: Box with Lid ................... 7
Defining a Table of Values.......................... 8
Zooming In on the Table ........................... 9
Changing the Viewing Window...................... 11
Displaying and Tracing the Graph ................... 12
Zooming In on the Graph........................... 13
Other TI-80 Features .............................. 14
Turning the TI-80 On and Off ....................... 1-2
Setting the Display Contrast ........................ 1-3
The Display ...................................... 1-4
Entering Expressions and Instructions ............... 1-6
The Edit Keys .................................... 1-8
Setting Modes .................................... 1-9
TI-80 Modes...................................... 1-10
Variable Names ................................... 1-12
Storing and Recalling Variable Values................ 1-13
Last Entry........................................ 1-14
Last Answer ...................................... 1-16
TI-80 Menus...................................... 1-17
The VARS and Y-VARS Menus...................... 1-19
EOS (Equation Operating System) .................. 1-20
Error Conditions ................................. 1-22
Table of Contents
Getting Started:
Do This First!
Chapter 1:
Operating the
TI-80

iv Introduction
Getting Started: Lottery Chances .................... 2-2
Using the TI-80 Functions .......................... 2-3
Keyboard Math Operations ......................... 2-4
MATH MATH Operations ........................... 2-7
MATH NUM (Number) Operations ................... 2-10
MATH PRB (Probability) Operations................. 2-12
ANGLE Operations ................................ 2-14
TEST (Relational) Operations....................... 2-16
Getting Started: Working with Fractions ............. 3-2
Setting Modes for Fraction Results .................. 3-4
Entering and Using Fractions in Calculations ......... 3-6
The FRACTION Menu.............................. 3-8
Getting Started: Graphing a Circle ................... 4-2
Defining a Graph.................................. 4-3
Setting Graph Modes .............................. 4-4
Defining Functions in the Y= List.................... 4-5
Evaluating Y= Functions in Expressions ............. 4-7
Selecting Functions ............................... 4-8
Defining the Viewing Window ...................... 4-9
Displaying a Graph ................................ 4-11
Exploring a Graph with the Free-Moving Cursor ...... 4-12
Exploring a Graph with TRACE ..................... 4-13
Exploring a Graph with ZOOM...................... 4-15
Setting the Zoom Factors .......................... 4-18
Getting Started: Path of a Ball ...................... 5-2
Defining and Displaying a Parametric Graph .......... 5-3
Exploring a Parametric Graph ...................... 5-6
Chapter 2:
Math, Angle, and
Test Operations
Chapter 3:
Fractions
Chapter 4:
Function
Graphing
Chapter 5:
Parametric
Graphing

Introduction v
Getting Started: Roots of a Function ................. 6-2
Defining the Independent Variable .................. 6-3
Defining the Dependent Variable .................... 6-4
Displaying the Table............................... 6-5
Getting Started: Shading a Graph.................... 7-2
DRAW DRAW Menu ............................... 7-3
Drawing Lines .................................... 7-4
Drawing Horizontal and Vertical Lines ............... 7-5
Drawing a Function ............................... 7-6
Shading Areas on a Graph .......................... 7-7
Drawing Points ................................... 7-10
Clearing a Drawing ................................ 7-12
Getting Started: Generating a Sequence .............. 8-2
About Lists....................................... 8-3
LIST OPS Operations .............................. 8-6
LIST MATH Operations ............................ 8-9
Getting Started: Building Height and City Size......... 9-2
Setting Up a Statistical Analysis..................... 9-8
The STAT List Editor .............................. 9-9
Viewing, Entering, and Editing Lists ................. 9-10
Sorting and Clearing Lists .......................... 9-13
Statistical Analysis ................................ 9-14
Types of Statistical Analysis ........................ 9-15
Statistical Variables ............................... 9-17
Statistical Plotting ................................ 9-18
Statistical Analysis in a Program .................... 9-22
Statistical Plotting in a Program..................... 9-23
Chapter 6:
Tables
Chapter 7:
Draw Operations
Chapter 8:
Lists
Chapter 9:
Statistics

vi Introduction
Getting Started: Rolling a Die ....................... 10-2
About TI-80 Programs ............................. 10-4
Creating and Executing Programs ................... 10-5
Editing Programs ................................. 10-6
PRGM CTL (Control) Instructions ................... 10-7
PRGM I/O (Input/Output) Instructions ............... 10-11
Calling Other Programs ............................ 10-14
Probability Experiments: Coins, Dice, and Spinners ... 11-2
The Unit Circle and Trigonometric Curves............ 11-3
Program: Newton’s Numerical Solve Routine ......... 11-4
Program: Numerical Integration..................... 11-6
Program: Window Variables Store and Recall ......... 11-8
Graphing the Inverse of a Function .................. 11-10
Graphing a Piecewise Function ..................... 11-12
Graphing Inequalities .............................. 11-14
Graphing a Polar Equation ......................... 11-15
Program: Guess the Coefficients .................... 11-16
Checking Available Memory ........................ 12-2
Deleting Items from Memory ....................... 12-3
Resetting the TI-80 ................................ 12-4
Chapter 10:
Programming
Chapter 11:
Applications
Chapter 12:
Memory
Management

Introduction vii
Table of TI-80 Functions and Instructions ............ A-2
Menu Map........................................ A-20
TI-80 Variables ................................... A-26
Battery Information ............................... B-2
Accuracy Information ............................. B-8
In Case of Difficulty ............................... B-10
Service and Support Information ................... B-14
Warranty Information.............................. B-15
Appendix A:
Tables and
Reference
Information
Appendix B:
Service and
Warranty
Information
Index

viii Introduction
The structure of the TI-80 guidebook and the design of its pages can help you
find the information you need quickly. Consistent presentation techniques are
used throughout to make the guidebook easy to use.
The guidebook is designed to teach you how to use the
calculator.
¦Getting Started is a fast-paced, keystroke-by-keystroke
introduction.
¦Chapter 1 describes general operation and lays the
foundation for Chapters 2 through 10, which describe
specific functional areas of the TI-80. Most chapters begin
with a brief Getting Started introduction.
¦Chapter 11 contains application examples that incorporate
features from different functional areas of the calculator.
These examples can help you see how different functional
areas work together to accomplish meaningful tasks.
¦Chapter 12 describes memory management.
When possible, units of information are presented on a single
page or on two facing pages. Several page-design elements
help you find information quickly.
¦Page headings—The descriptive heading at the top of the
page or two-page unit identifies the subject of the unit.
¦General text—Just below the page heading, a short
section of bold text provides general information about
the subject covered in the unit.
¦Left-column subheadings—Each subheading identifies a
specific topic or task related to the page or unit subject.
Using this Guidebook Effectively
Structure of the
Guidebook
Page-Design
Conventions

Introduction ix
¦Specific text—The text to the right of a subheading
presents detailed information about that specific topic or
task. The information may be presented as paragraphs,
numbered procedures, bulleted lists, or illustrations.
¦Page “footers”—The bottom of each page shows the
chapter name, chapter number, and page number.
Several conventions are used to present information concisely
and in an easily referenced format.
¦Numbered procedures—A procedure is a sequence of
steps that performs a task. In this guidebook, each step is
numbered in the order in which it is performed. No other
text in the guidebook is numbered; therefore, when you
see numbered text, you know you should perform the
steps sequentially.
¦Lists with bullets—If several items have equal
importance, or if you may choose one of several
alternative actions, this guidebook precedes each item
with a “bullet” (¦) to highlight it—like this list.
¦Tables and charts—Sets of related information are
presented in tables or charts for quick reference.
¦Keystroke examples—The Getting Started examples
provide keystroke-by-keystroke instructions, as do the
numerous short examples and several detailed examples
that are identified with a .
Information-
Mapping
Conventions

x Introduction
Several techniques have been used to help you look up
specific information when you need it. These include:
¦A chapter table of contents on the first page of each
chapter, as well as the full table of contents at the front of
the guidebook.
¦A glossary at the end of this section, defining important
terms used throughout the guidebook.
¦An alphabetical table of functions and instructions in
Appendix A, showing their correct formats, how to access
them, and page references for more information.
¦Information about system variables in Appendix A.
¦A table of error messages in Appendix B, showing the
messages and their meanings and giving problem-handling
information.
¦An alphabetical index at the back of the guidebook, listing
tasks and topics you may need to look up.
Reference Aids

Introduction xi
This glossary provides definitions for important terms that are used throughout
this guidebook.
An argument is an input upon which the value of a function
depends.
A command is any entry submitted to the calculator using
¸. There are two types of TI-80 commands: instructions
and expressions.
An expression is a complete sequence of numbers, variables,
functions, and their arguments that can be evaluated to a
single answer. An expression returns the evaluated result to
ANS.
A function, which may have arguments, returns a value and
can be used in an expression.
A function is also the expression entered in the Y= editor used
in graphing.
The Home screen is the primary screen of the TI-80, where
expressions can be entered and evaluated and instructions
can be entered and executed.
An instruction, which may have arguments, initiates an action.
Instructions are not valid in expressions. An instruction does
not return a value to ANS.
A list is a set of values that the TI-80 can use for activities
such as evaluating a function at multiple values and entering
statistical data.
Menu items are shown on full-screen menus.
Glossary
Argument
Command
Expression
Function
Home Screen
Instruction
List
Menu Items

xii Introduction
A pixel (picture element) is a square dot on the TI-80 display.
The TI-80 display is 64 pixels wide and 48 pixels high.
On the TI-80, real numbers are individual decimal or fraction
values.
A value is a single decimal or fraction number or a list of
decimals or fractions.
A variable is the name given to a location in memory in which
a value, an expression, a list, or another named item is stored.
Pixel
Real Number
Value
Variable

Getting Started 1
Getting Started contains two keystroke-by-keystroke examples

an interest rate
problem and a volume problem

which introduce you to some principal
operating and graphing features of the TI.80. You will learn to use the TI.80 more
quickly by completing both of these examples first.
TI-80 Keyboard ................................... 2
First Steps ....................................... 3
TI-80 Menus...................................... 4
Entering a Calculation: Compound Interest ........... 5
Continuing a Calculation ........................... 6
Defining a Function: Box with Lid ................... 7
Defining a Table of Values.......................... 8
Zooming In on the Table ........................... 9
Changing the Viewing Window...................... 11
Displaying and Tracing the Graph ................... 12
Zooming In on the Graph........................... 13
Other TI-80 Features .............................. 14
Getting Started: Do This First!
Contents

2 Getting Started
The keys on the TI.80 are grouped by color and physical layout to allow easy
location of the key you need. The keys are divided into zones: graphing keys,
editing keys, advanced function keys, and scientific calculator keys.
Graphing &
Editing &
Advanced &
Functions
Scientific &
Calculator
These keys are most frequently used to access the interactive
graphing features of the TI-80.
These keys are most frequently used for editing expressions
and values.
These keys are most frequently used to access the advanced
functions of the TI-80.
These keys are most frequently used to access the capabilities
of a standard scientific calculator.
TI-80 Keyboard
The Zones of the
Keyboard
Graphing Keys
Editing Keys
Advanced
Function Keys
Scientific
Calculator Keys

Getting Started 3
Before beginning the two sample problems, follow the steps on this page to
reset the TI-80 to its factory settings. (Resetting the TI-80 erases all previously
entered data.) This ensures that following the keystrokes in this section
produces the same actions.
1. Press ´to turn the calculator on.
If the screen is very dark or blank, adjust the display
contrast. Press and release 2, and then press and
hold 8(to make the display lighter) or press and
hold 7(to make the display darker). You can press
Mto clear the display.
E
x
2. Press and release 2, and then press µ. (Pressing
2gives you access to the 2nd operations, which are
printed at the upper left of the keys. MEM is the
2nd operation of the µkey.)
The MEMORY menu is displayed.
3. Press 3to select RESET... from the MEMORY menu.
The MEMORY RESET menu is displayed.
4. Press 2to select RESET from the MEMORY RESET
menu. The calculator is reset, and the
MEM CLEARED message is displayed.
First Steps

4 Getting Started
To leave the keyboard uncluttered, the TI.80 uses full-screen menus to display
many additional operations. The use of specific menus is described in the
appropriate chapters.
Displaying a Menu
When you press a key that displays a menu, such as
I, that menu screen temporarily replaces the screen
where you are working.
A
fter you make a selection from a menu, you usually are
returned to the screen where you were.
Moving from One Menu to Another
A
menu key may display more than one menu name. The
names appear on the top line. The name of current menu
is highlighted, and the items in that menu are displayed.
Use 9or 6to display a different menu.
Selecting an Item from a Menu
The number of the current item is highlighted. If there are
more than seven items on the menu, a $appears on the
last line in place of the : (colon).
To select from a menu, you can either:
¦Use 8and 7to move the cursor to the item, and
then press ¸.
¦Press the number of the item.
Note: The tenth item in a menu is number 0. If there are
more than 10 items, they are numbered A, B, C, etc. To
select one of these items, press ?and then the
letter.
Leaving without Making a Selection
To leave a menu without making a selection:
¦Press 2.to return to the Home screen.
¦Press Mto return to the screen where you
were.
¦Press the key for another screen or menu.
TI-80 Menus

Getting Started 5
The TI.80 displays up to 8 16-characters lines so that you see an expression and
its solution together. You can store values to variables, enter multiple
instructions on one line, and recall previous entries.
Using trial and error, determine when an amount invested at 6% annual
compounded interest will double in value.
1. For the first guess, compute the amount available at
the end of 10 years. Enter the expression just as you
would write it. (Use 1000 for the amount.)
Press 1000 p1.06 Z10.
2. Press ¸to evaluate the expression.
The answer is shown on the right side of the display.
The cursor is positioned on the next line, ready for
you to enter the next expression.
3. The next guess should be greater than 10 years. Make
the next guess 12 years. To calculate the amount after
12 years, press 1000 p1.06 Z12, followed by ¸.
Entering a Calculation: Compound Interest

6 Getting Started
To save keystrokes, you can use the Last Entry feature to recall the last
expression entered and then edit it for a new calculation. In addition, the next
expression can be continued from the previous result.
1. The next guess should be less than, but close to, 12
years. Compute the amount available at the end of
11.9 years, using the Last Entry feature. Press 2,
followed by ²(the second function of ¸).
The last calculated expression is shown on the next
line of the display. The cursor is positioned at the end
of the expression.
2. You can edit the expression. Press 6to move the
cursor over the 2. Then type 1.9 to change 12 to 11.9.
Press ¸to evaluate the expression.
Note: This process can be continued to obtain a
solution with the desired accuracy.
3. You can continue a calculation using the result of the
last calculation. For example, if the final amount
determined above is to be divided among seven
people, how much would each person get?
To divide the last calculation by seven, press e7,
followed by ¸.
As soon as you press e, ANSàis displayed at the
beginning of the new expression. ANS is a variable
that contains the last calculated result. In this case,
ANS contains 2000.505716.
Continuing a Calculation

Getting Started 7
Take an 8½"×11" sheet of paper and cut X by X squares from two corners and X
by (X+B) rectangles from the other two corners. Now fold the paper into a box
with lid. What X would give the maximum volume V of a box made in this way?
Use tables and graphs to determine the solution.
Begin by defining a function that describes the
volume of the box.
From the diagram: 2X + A = W
2X + 2B = L
V = A B X
Substituting: V = (W – 2X) (L à2 – X) X
W
X
X
A
BXB
L
If necessary, press z†Íto change the
MODE to FLOAT. Then press y.‘to
return to the Home screen and clear it.
1. Press 8.5 ¿ƒWÍto store the width of
the paper.
Press 11 ¿ƒL Íto store the length of
the paper.
2. You define functions for tables and graphs on the Y=
edit screen.
Press oto access this screen.
3. Enter the function for volume as Y1. Press £ƒ
W¹2@¤£ƒL¥2¹@¤@Í
to define function Y1 in terms of X. (@lets you
enter Xquickly without pressing ƒ.)
The =sign is highlighted to show that Y1 is selected.
Defining a Function: Box with Lid

8 Getting Started
The table feature of the TI.80 provides numeric information about a function.
Use a table of values from the previously defined function to estimate an answer
to the problem.
1. Press y#(above p) to display the
TABLE SETUP screen.
2. Press Íto accept TBLMIN=0.
3. Press .5 Íto define the table increment @TBL=.5.
4. Press y&(above s) to display the table.
Note that the maximum value is around 1.5, between
1and 2.
5. Press and hold †to scroll the table until the sign
change appears. Note that the maximum length of X
for this problem occurs where the sign of Y1
(volume) becomes negative.
6. Press y#. Note that TBLMIN has changed to
reflect the first line of the table you last displayed.
Defining a Table of Values