Texas Instruments TI-89 user guide: Chapter 1: Getting Started

Chapter 1: Getting Started

Expanding Expressions

1. Expand the expression (x–5)³.
   • You can enter “expand” on the entry line by typing EXPAND on the keyboard, or by pressing F2 and selecting 3:expand(.

2. (Optional) Enter other expressions on your own.

Reducing Expressions

1. Reduce the expression (x²–2x–5)/(x–1) to its simplest form.
   • You can enter “propFrac” on the entry line by typing PROPFRAС on the keyboard, or by pressing F2 and selecting 7:propFrac(.

Factoring Polynomials

1. Factor the polynomial (x²–5) with respect to x.
   • You can enter “factor” on the entry line by typing FACTOR on the keyboard or by pressing F2 and selecting 2:factor(.

Solving Equations

1. Solve the equation x²–2x–6=2 with respect to x.
   • You can enter “solve(” on the entry line by selecting “solve(” from the Catalog menu, by typing SOLVE( on the keyboard, or by pressing F2 and selecting 1:solve(.
   • The status line area shows the required syntax for the marked item in the Catalog menu.

10 Chapter 1: Getting Started

Graphing a Function

The example in this section demonstrates some of the graphing capabilities of the TI-89 / TI-92 Plus. It illustrates how to graph a function using the Y= Editor. You will learn how to enter a function, produce a graph of the function, trace a curve, find a minimum point, and transfer the minimum coordinates to the Home screen.

Explore the graphing capabilities of the TI-89 / TI-92 Plus by graphing the function y=(|x²– 3|– 10)/2.

\begin{tabular}{|l|l|l|l|} \hline Steps & TI-89 Keystrokes & TI-92 Plus Keystrokes & Display \ \hline

1. Display the Y= Editor. & \blacklozenge [Y=] & \blacklozenge [Y=] & \ \hline
2. Enter the function (abs(x$^2$– 3) – 10)/2. & \square CATALOG A ENTER X\square 2 \square 3 \square \square 10 \square \square 2 ENTER & \square 2nd CATALOG A ENTER X\wedge 2 \square 3 \square \square 10 \square \square 2 ENTER & "pretty print" display of the function in the entry line \ \hline
3. Display the graph of the function. \newline Select 6:ZoomStd by pressing 6 or by moving the cursor to 6:ZoomStd and pressing ENTER. & F2 6 & F2 6 & \ \hline
4. Turn on Trace. \newline The tracing cursor, and the x and y coordinates are displayed. & F3 & F3 & tracing cursor \ \hline
5. Open the MATH menu and select 3:Minimum. & F5 \circlearrowleft \circlearrowright ENTER & F5 \circlearrowleft \circlearrowright ENTER & \ \hline \end{tabular}

Chapter 1: Getting Started 11

12 Chapter 1: Getting Started

Operating the Calculator

Chapter 2: Operating the Calculator

This chapter gives a general overview of the TI-89 / TI-92 Plus and describes its basic operations. By becoming familiar with the information in this chapter, you can use the TI-89 / TI-92 Plus to solve problems more effectively.

The Home screen is the most commonly used application on the TI-89 / TI-92 Plus. You can use the Home screen to perform a wide variety of mathematical operations.

Table of Contents

• Turning the TI-89 / TI-92 Plus On and Off ........ 14
• Setting the Display Contrast ........ 15
• The TI-89 Keyboard ........ 16
• The TI-92 Plus Keyboard ........ 17
• Modifier Keys ........ 18
• Entering Alphabetic Characters ........ 21
• Home Screen ........ 23
• Entering Numbers ........ 25
• Entering Expressions and Instructions ........ 26
• Formats of Displayed Results ........ 29
• Editing an Expression in the Entry Line ........ 32
• Menus ........ 34
• Using the Custom Menu ........ 37
• Selecting an Application ........ 38
• Setting Modes ........ 40
• Using the Clean Up Menu to Start a New Problem ........ 43
• Using the Catalog Dialog Box ........ 44
• Storing and Recalling Variable Values ........ 47
• Reusing a Previous Entry or the Last Answer ........ 49
• Auto-Pasting an Entry or Answer from the History Area ........ 52
• Status Line Indicators in the Display ........ 53
• Finding the Software Version and ID Number ........ 55

Turning the TI-89 / TI-92 Plus On and Off

You can turn the TI-89 / TI-92 Plus on and off manually by using the [ON] and [2nd] [OFF] (or [♦] [OFF]) keys. To prolong battery life, the APD™ (Automatic Power Down™) feature lets the TI-89 / TI-92 Plus turn itself off automatically.

Turning the TI-89 / TI-92 Plus On

Press [ON].

• If you turned the unit off by pressing [2nd] [OFF], the TI-89 / TI-92 Plus returns to the Home screen.
• If you turned the unit off by pressing [♦] [OFF] or if the unit turned itself off through APD, the TI-89 / TI-92 Plus returns to whichever application you used last.

Turning the TI-89 / TI-92 Plus Off

Note: [OFF] is the second function of the [ON] key.

You can use either of the following keys to turn off the TI-89 / TI-92 Plus.

APD (Automatic Power Down)

After several minutes without any activity, the TI-89 / TI-92 Plus turns itself off automatically. This feature is called APD.

When you press [ON], the TI-89 / TI-92 Plus will be exactly as you left it.

• The display, cursor, and any error conditions are exactly as you left them.
• All settings and memory contents are retained.

APD does not occur if a calculation or program is in progress, unless the program is paused.

Batteries

The TI-89 uses four AAA alkaline batteries and a back-up lithium battery. The TI-92 Plus uses four AA alkaline batteries and also has a back-up lithium battery. To replace the batteries in either calculator without losing any information stored in memory, follow the directions in Appendix C.

14 Chapter 2: Operating the Calculator

Setting the Display Contrast

The brightness and contrast of the display depend on room lighting, battery freshness, viewing angle, and the adjustment of the display contrast. The contrast setting is retained in memory when the TI-89 / TI-92 Plus is turned off.

Adjusting the Display Contrast

You can adjust the display contrast to suit your viewing angle and lighting conditions.

TI-89 contrast keys

TI-92 Plus contrast keys

If you press and hold ◆ □ or ◆ □ too long, the display may go completely black or blank. To make finer adjustments, hold ◆ and then tap □ or □.

When to Replace Batteries

Tip: The display may be very dark after you change batteries. Use ◆ □ to lighten the display.

As the batteries get low, the display begins to dim (especially during calculations) and you must increase the contrast. If you have to increase the contrast frequently, replace the four alkaline batteries.

The status line along the bottom of the display also gives battery information.

Using the TI-92 Plus Cover as a Stand

When using the TI-92 Plus on a desk or table top, you can use the snap-on cover to prop up the unit at one of three angles. This may make it easier to view the display under various lighting conditions.

Note: Slide the tabs at the top-sides of the TI-92 Plus into the slots in the cover.

Chapter 2: Operating the Calculator 15

The TI-89 Keyboard

Use this section to familiarize yourself with the various keys on the TI-89 keyboard. Most keys can perform two or more functions, depending on whether you first press a modifier key.

Overview of Some Important Keys

[F1] through [2nd] [F8] function keys let you select toolbar menus. Used with [◄], you can also select applications (page 39).

[2nd], [▲], [▼], and [alpha] modify the action of other keys (page 18).

[HOME] displays the Home screen, where you perform most calculations.

X, Y, and Z are often used in symbolic calculations.

[MODE] lets you view and change mode settings that determine how numbers and graphs are interpreted, calculated, and displayed (page 40).

[Texas Instruments] [TI-89]

[F1] [F2] [F3] [F4] [F5]

[2nd] [↑] [ESC] { lock [◆] [alpha] [APPS]

[CUSTOM] [HOME] [MODE] [CATALOG] [←] [CLEAR]

[X] [Y] [Z] [T] [∧] [=] [(] [)] [,] [÷] [1] [7] [8] [9] [×] [EE] [4] [5] [6] [-] [STO►] [1] [2] [3] [+] [ON] [0] [·] [(—)] [ENTER]

[ESC] cancels a menu or dialog box.

(◄), (►), (▲), and (▼) move the cursor.

[APPS] lets you select an application (page 38).

[CLEAR] erases the entry line. Also used to delete an entry/answer pair in the history area.

[CATALOG] lets you select from a list of functions and instructions (page 44).

Adjust the contrast by pressing [◆] [−] (lighten) or [◆] [+] (darken).

[ENTER] evaluates an expression, executes an instruction, selects a menu item, etc.

You can use [◆] [ENTER] to display an approximate numerical result.

Moving the Cursor

To move the cursor in a particular direction, press the appropriate cursor key ((◄), (►), (▲), or (▼)).

Some TI-89 applications also let you press:

• [2nd] (◄) or [2nd] (►) to move to the beginning or end of a line. • [2nd] (▲) or [2nd] (▼) to move up or down one screen at a time. • [◆] (▲) or [◆] (▼) to move to the top or bottom of a page. • (►) and (▲), (►) and (▼), (◄) and (▲), or (◄) and (▼) to move diagonally. (Press the indicated cursor keys simultaneously.)

16 Chapter 2: Operating the Calculator

The TI-92 Plus Keyboard

With the TI-92 Plus's easy-to-hold shape and keyboard layout, you can quickly access any area of the keyboard even when you are holding the unit with two hands.

Keyboard Areas

The keyboard is divided into several areas of related keys.

Function Keys Access the toolbar menus displayed across the top of the screen.

Cursor Pad Moves the display cursor in up to 8 directions, depending on the application.

Application Shortcut Keys Used with the [icon] key to let you select commonly used applications.

QWERTY Keyboard Enters text characters just as you would on a typewriter.

Calculator Keypad Performs a variety of math and scientific operations.

Cursor Pad

To move the cursor, press the applicable edge of the cursor pad. This guidebook uses key symbols such as [up arrow icon] and [right arrow icon] to indicate which side of the cursor pad to press.

For example, press [right arrow icon] to move the cursor to the right.

Note: The diagonal directions ([diagonal arrow icon], etc.) are used only for geometry and graphing applications.

Chapter 2: Operating the Calculator 17

Modifier Keys

Modifier Keys

Note: For information about using ↑ and [alpha], refer to “Entering Alphabetic Characters” on page 21.

Examples of [2nd] and ◆ Modifiers

The [ESC] key is one of several keys that can perform three operations, depending on whether you first press [2nd] or ◆.

The following TI-89 example shows using the [2nd] or ◆ modifier key with the [ESC] key.

[2nd] [QUIT] accesses QUIT, which is the same color as the [2nd] key. QUIT PASTE ESC | [ESC] accesses the key’s primary function.

◆ [PASTE] accesses PASTE, which is the same color as the ◆ key.

The following TI-92 Plus example shows using the [2nd] or ◆ modifier key with the Y alphabetic key.

[2nd] [►] accesses ► (convert). The convert symbol is the same color as the [2nd] key. ► TABLE Y | Pressing the primary key types the letter Y.

◆ [TABLE] displays the Table screen. The word is the same color as the ◆ key.

18 Chapter 2: Operating the Calculator

Some keys perform only one additional operation, which may require either 2nd or ♦, depending on the color in which the operation is printed on the keyboard and where it is positioned above the key.

On the TI-89, ♦ [CUT] accesses CUT, which is the same color as the ♦ key.

When you press a modifier such as 2nd or ♦, a 2ND or ♦ indicator appears in the status line at the bottom of the display. If you press a modifier by accident, press it again (or press [ESC]) to cancel its effect.

Other Important Keys You Need to Be Familiar With

Note: Some keystrokes differ between the TI-89 and the TI-92 Plus. See the Keystroke Differences table in the front of this guidebook for a complete list.

Chapter 2: Operating the Calculator 19

Important Keys (continued)

20 Chapter 2: Operating the Calculator

Entering Alphabetic Characters

Alphabetic characters are used in expressions such as x²+y², to enter variable names (page 47), and in the Text Editor (Chapter 18).

Entering a Letter Character on the TI-89

The letters x, y, z, and t are commonly used in algebraic expressions. So that you can type them quickly, these letters are primary keys on the TI-89 keyboard.

[X] [Y] [Z] [T]

Other letters are available as the [alpha] function of another key, similar to the [2nd] and [♦] modifiers described in the previous section. For example:

[2nd] ['] types ', which is the same color as the [2nd] key.
[alpha] [A] types an A, which is the same color as the [alpha] key.

Typing Alphabetic Characters on the TI-89 / TI-92 Plus

Note: On the TI-89, you do not need [alpha] or alpha-lock to type x, y, z, or t. But you must use [↑] or uppercase ALPHA-lock for X, Y, Z, or T.

Note: On the TI-89, alpha-lock is always turned off when you change applications, such as going from the Text Editor to the Home screen.

Chapter 2: Operating the Calculator 21

Typing Alphabetic Characters ... (continued)

On the TI-89, while either type of alpha-lock is on:

• To type a period, comma, or other character that is the primary function of a key, you must turn alpha-lock off.
• To type a second function character such as \underline2nd [()], you do not need to turn alpha-lock off. After you type the character, alpha-lock remains on.

Automatic Alpha-Lock in TI-89 Dialog Boxes

There are certain times when you do not need to press \underlinealpha or \underline2nd [a-lock] to type alphabetic characters on the TI-89. Automatic alpha-lock is turned on whenever a dialog box is first displayed. The automatic alpha-lock feature applies to these dialog boxes:

\begin{tabular}{ll} \hline Dialog box & Alpha-lock \ \hline Catalog dialog box & All commands are listed in alphabetical order. Press a letter to go to the first command that begins with that letter. See page 44 for more information. \ Units dialog box & In each unit category, type the first letter of a unit or constant. See Chapter 4 for more information. \ Dialog boxes with entry fields & These include, but are not limited to: Create New Folder, Rename, and Save Copy As. See page 35 for more information about dialog boxes. \ \hline \end{tabular}

Note: To type a number, press \underlinealpha to turn alpha-lock off. Press \underlinealpha or \underline2nd [a-lock] to resume typing letters.

Alpha-lock is not turned on in dialog boxes that require numeric-only entries. The dialog boxes that accept only numeric entries are: Resize Matrix, Zoom Factors, and Table Setup.

For Special Characters

Use the \underline2nd [CHAR] menu to select from a variety of special characters. For more information, refer to "Entering Special Characters" in Chapter 18.

22 Chapter 2: Operating the Calculator

Home Screen

When you first turn on your TI-89 / TI-92 Plus, the Home screen is displayed. The Home screen lets you execute instructions, evaluate expressions, and view results.

Displaying the Home Screen

When you turn on the TI-89 / TI-92 Plus after it has been turned off with [2nd] [OFF], the display always shows the Home screen. (If the TI-89 / TI-92 Plus turned itself off through APD™, the display shows the previous screen, which may or may not have been the Home screen.)

To display the Home screen at any time:

• Press:
  • TI-89: [HOME]
  • TI-92 Plus: [♦] [HOME]
  • — or —
• Press [2nd] [QUIT]
  • — or —
• Press:
  • TI-89: [APPS] [alpha] A
  • TI-92 Plus: [APPS] A

Parts of the Home Screen

The following example gives a brief description of the main parts of the Home screen.

History Area Lists entry/answer pairs you have entered.

F1+ F2+ F3+ F4+ F5 F6+ Tools Algebra Calc Diffs Fr3 Pol□ Cls□ Up

■ 1.7^4.2 7.14 ■ 5.4/.7 .771429 ■ cos(π/4) √2/2 cos(π/4) MAIN RAD AUTO FUNC 3/30

Pretty Print Display Shows exponents, roots, fractions, etc., in traditional form. Refer to page 29.

Last Entry Your last entry.

Entry Line Where you enter expressions or instructions.

Toolbar Press [F1], [F2], etc., to display menus for selecting operations.

Last Answer Result of your last entry. Note that results are not displayed on the entry line.

Status Line Shows the current state of the TI-89 / TI-92 Plus.

History Area

The history area shows up to eight previous entry/answer pairs (depending on the complexity and height of the displayed expressions). When the display is filled, information scrolls off the top of the screen. You can use the history area to:

• Review previous entries and answers. You can use the cursor to view entries and answers that have scrolled off the screen.
• Recall or auto-paste a previous entry or answer onto the entry line so that you can re-use or edit it. Refer to pages 50 and 52.

Chapter 2: Operating the Calculator 23

Scrolling through the History Area

Normally, the cursor is in the entry line. However, you can move the cursor into the history area.

Note: For an example of viewing a long answer, refer to page 28.

History Information on the Status Line

Use the history indicator on the status line for information about the entry/answer pairs. For example:

If the cursor is on the entry line:

• Total number of pairs that are currently saved.
• Maximum number of pairs that can be saved.
• □/□□

If the cursor is in the history area:

• Pair number of the highlighted entry or answer.
• Total number of pairs that are currently saved.

By default, the last 30 entry/answer pairs are saved. If the history area is full when you make a new entry (indicated by 30/30), the new entry/answer pair is saved and the oldest pair is deleted. The history indicator does not change.

Modifying the History Area

24 Chapter 2: Operating the Calculator

Entering Numbers

The keypad lets you enter positive and negative numbers for your calculations. You can also enter numbers in scientific notation.

Entering a Negative Number

1. Press the negation key [(-)]. (Do not use the subtraction key [-].)
2. Type the number.

To see how the TI-89 / TI-92 Plus evaluates a negation in relation to other functions, refer to the Equation Operating System (EOS™) hierarchy in Appendix B. For example, it is important to know that functions such as $x^2$ are evaluated before negation.

Use ( and ) to include parentheses if you have any doubt about how a negation will be evaluated.

Important: Use [-] for subtraction and use [(-)] for negation.

Evaluated as -(2²) ■ -2² -4 ■ (-2)² 4 ( -2 ) ^ 2 MIN RAD AUTO FUNC 2/30

If you use [-] instead of [(-)] (or vice versa), you may get an error message or you may get unexpected results. For example:

• 9 [×] [(-)] 7 = -63 — but — 9 [×] [-] 7 displays an error message.
• 6 [-] 2 = 4 — but — 6 [(-)] 2 = -12 since it is interpreted as 6(-2), implied multiplication.
• [(-)] 2 [+] 4 = 2 — but — [-] 2 [+] 4 subtracts 2 from the previous answer and then adds 4.

Entering a Number in Scientific Notation

1. Type the part of the number that precedes the exponent. This value can be an expression.
2. Press: TI-89: [EE] TI-92 Plus: [2nd] [EE] E appears in the display.
3. Type the exponent as an integer with up to 3 digits. You can use a negative exponent.

Entering a number in scientific notation does not cause the answers to be displayed in scientific or engineering notation.

The display format is determined by the mode settings (pages 29 through 31) and the magnitude of the number.

■ 1.2345 1.2345 123.45E^-2 MIN RAD AUTO FUNC 1/30 Represents 123.45 × 10⁻²

Chapter 2: Operating the Calculator 25

Entering Expressions and Instructions

You perform a calculation by evaluating an expression. You initiate an action by executing the appropriate instruction. Expressions are calculated and results are displayed according to the mode settings described on page 29.

Definitions

Expression Consists of numbers, variables, operators, functions, and their arguments that evaluate to a single answer. For example: \pi r^2 + 3.

• Enter an expression in the same order that it normally is written.
• In most places where you are required to enter a value, you can enter an expression.

Operator Performs an operation such as $+$, $-$, $*$, ^\wedge.

• Operators require an argument before and after the operator. For example: 4+5 and 5^2.

Note: Appendix A describes all of the TI-89 / TI-92 Plus built-in functions and instructions.

Function Returns a value.

• Functions require one or more arguments (enclosed in parentheses) after the function. For example: \sqrt(5) and min(5,8).

Note: This guidebook uses the word command as a generic reference to both functions and instructions.

Instruction Initiates an action.

• Instructions cannot be used in expressions.
• Some instructions do not require an argument. For example: ClrHome.
• Some require one or more arguments. For example: Circle 0,0,5.
  • For instructions, do not put the arguments in parentheses.

Implied Multiplication

The TI-89 / TI-92 Plus recognizes implied multiplication, provided it does not conflict with a reserved notation.

\begin{tabular}{lll} & If you enter: & The TI-89 / TI-92 Plus interprets it as: \ Valid & 2\pi & 2*\pi \ & 4 sin(46) & 4sin(46) \ & 5(1+2) or (1+2)5 & 5(1+2) or (1+2)5 \ & [1,2]a & [a 2a] \ & 2(a) & 2a \ Invalid & xy & Single variable named xy \ & a(2) & Function call \ & a[1,2] & Matrix index to element a[1,2] \ \end{tabular}

26 Chapter 2: Operating the Calculator

Parentheses

Expressions are evaluated according to the Equation Operating System (EOS™) hierarchy described in Appendix B. To change the order of evaluation or just to ensure that an expression is evaluated in the order you require, use parentheses.

Calculations inside a pair of parentheses are completed first. For example, in 4(1+2), EOS first evaluates (1+2) and then multiplies the answer by 4.

Entering an Expression

Type the expression, and then press ENTER to evaluate it. To enter a function or instruction name on the entry line, you can:

• Press its key, if available. For example, press TI-89: 2nd [SIN] or TI-92 Plus: [SIN]. — or —
• Select it from a menu, if available. For example, select 2:abs from the Number submenu of the MATH menu. — or —
• Type the name letter-by-letter from the keyboard. (On the TI-89, use alpha and 2nd [a-lock] to type letters.) You can use any mixture of uppercase or lowercase letters. For example, type sin( or Sin(.

Example

Calculate 3.76 \div (-7.9 + \sqrt5) + 2 \log 45.

Type the function name in this example.

Note: You can also select log by using TI-89: CATALOG TI-92 Plus: 2nd [CATALOG] (page 44).

\begin{tabular}{|l|l|l|} \hline On the TI-89: & On the TI-92 Plus: & Display \ \hline 3.76 \rightarrow & 3.76 \rightarrow & 3.76/(-7.9+\sqrt( \ [(-)] 7.9 & [(-)] 7.9 & 2nd [\sqrt] inserts \sqrt (because its argument must be in parentheses. \ $[+]$ 2nd [\sqrt] & $[+]$ 2nd [\sqrt] & \ $5$ ) ) & $5$ ) ) & 3.76/(-7.9+\sqrt(5)) \ & & Use ) once to close \sqrt(5) and again to close (-7.9+\sqrt5). \ $[+] 2$ & $[+] 2$ & 3.76/(-7.9+\sqrt(5))+21og(45) \ 2nd [a-lock] L O G alpha & L O G & log requires () around its argument. \ [(-) 4 5 ] ) & [(-) 4 5 ] ) & \ ENTER & ENTER & \ \hline \end{tabular}

Entering Multiple Expressions on a Line

To enter more than one expression or instruction at a time, separate them with a colon by pressing 2nd [:].

Displays last result only.

\rightarrow is displayed when you press STO\rightarrow to store a value to a variable.

Chapter 2: Operating the Calculator 27

If an Entry or Answer Is Too Long for One Line

In the history area, if both the entry and its answer cannot be displayed on one line, the answer is displayed on the next line.

If an entry or answer is too long to fit on one line, ▶ is displayed at the end of the line.

To view the entire entry or answer:

1. Press ◀ to move the cursor from the entry line up into the history area. This highlights the last answer.
2. As necessary, use ◀ and ▶ to highlight the entry or answer you want to view. For example, ◀ moves from answer to entry, up through the history area.
3. Use ▶ and ◀ or [2nd] ▶ and [2nd] ◀ to scroll right and left.
4. To return to the entry line, press [ESC].

Note: When you scroll to the right, ◀ is displayed at the beginning of the line.

Continuing a Calculation

When you press [ENTER] to evaluate an expression, the TI-89 / TI-92 Plus leaves the expression on the entry line and highlights it. You can continue to use the last answer or enter a new expression.

Example

Calculate 3.76 ÷ (–7.9 + √5). Then add 2 log 45 to the result.

Stopping a Calculation

When a calculation is in progress, BUSY appears on the right end of the status line. To stop the calculation, press [ON].

There may be a delay before the “break” message is displayed.

Press [ESC] to return to the current application.

28 Chapter 2: Operating the Calculator

Formats of Displayed Results

A result may be calculated and displayed in any of several formats. This section describes the TI-89 / TI-92 Plus modes and their settings that affect the display formats. To check or change your current mode settings, refer to page 40.

Pretty Print Mode

By default, Pretty Print = ON. Exponents, roots, fractions, etc., are displayed in the same form in which they are traditionally written. You can use MODE to turn pretty print off and on.

Pretty Print ON OFF

\pi^2, \pi/2, \sqrtx-3/2 \pi\wedge2, \pi/2, \sqrt((x-3)/2)

The entry line does not show an expression in pretty print. If pretty print is turned on, the history area will show both the entry and its result in pretty print after you press ENTER.

Exact/Approx Mode

By default, Exact/Approx = AUTO. You can use MODE to select from three settings.

Because AUTO is a combination of the other two settings, you should be familiar with all three settings.

1:1AUTO 2:1EXACT 3:3APPROXIMATE

Note: By retaining fractional and symbolic forms, EXACT reduces rounding errors that could be introduced by intermediate results in chained calculations.

EXACT — Any result that is not a whole number is displayed in a fractional or symbolic form (1/2, \pi, \sqrt2, etc.).

■ 2.5.2 5 ■ 2.5.3 15/2 ■ 6.3 2 ■ 6.4 3/2 6/4 MAIN RAD EXACT FUNC 4/20

Shows whole-number results.

Shows simplified fractional results.

■ 2. \pi 2. \pi ■ \frac\sqrt22 \frac\sqrt22 ■ \sqrt47 \frac2\sqrt77 \sqrt(47) MAIN RAD EXACT FUNC 3/20

Shows symbolic \pi.

Shows symbolic form of roots that cannot be evaluated to a whole number.

■ \sqrt47 \frac2\sqrt77 ■ \sqrt47 .755929 \sqrt(47) MAIN RAD EXACT FUNC 4/20

Press \blacklozenge [ENTER] to temporarily override the EXACT setting and display a floating-point result.

Chapter 2: Operating the Calculator 29

Exact/Approx (continued)

APPROXIMATE — All numeric results, where possible, are displayed in floating-point (decimal) form.

Note: Results are rounded to the precision of the TI-89 / TI-92 Plus and displayed according to current mode settings.

Because undefined variables cannot be evaluated, they are treated algebraically. For example, if the variable r is undefined, πr² = 3.14159·r².

AUTO — Uses the EXACT form where possible, but uses the APPROXIMATE form when your entry contains a decimal point. Also, certain functions may display APPROXIMATE results even if your entry does not contain a decimal point.

Tip: To retain an EXACT form, use fractions instead of decimals. For example, use 3/2 instead of 1.5.

The following chart compares the three settings.

Tip: To evaluate an entry in APPROXIMATE form, regardless of the current setting, press ◄ [ENTER].

30 Chapter 2: Operating the Calculator

Display Digits Mode

By default, Display Digits = FLOAT 6, which means that results are rounded to a maximum of six digits. You can use MODE to select different settings. The settings apply to all exponential formats.

Internally, the TI-89 / TI-92 Plus calculates and retains all decimal results with up to 14 significant digits (although a maximum of 12 are displayed).

Note: Regardless of the Display Digits setting, the full value is used for internal floating-point calculations to ensure maximum accuracy.

\begin{tabular}{lll} \hline Setting & Example & Description \ \hline FIX & 123. & (FIX 0) Results are rounded to the \ (0 – 12) & 123.5 & (FIX 1) selected number of decimal \ & 123.46 & (FIX 2) places. \ & 123.457 & (FIX 3) \ FLOAT & 123.456789012 & Number of decimal places varies, \ & & depending on the result. \ FLOAT & 1.E 2 & (FLOAT 1) Results are rounded to the total \ (1 – 12) & 1.2e 2 & (FLOAT 2) number of selected digits. \ & 123. & (FLOAT 3) \ & 123.5 & (FLOAT 4) \ & 123.46 & (FLOAT 5) \ & 123.457 & (FLOAT 6) \ \hline \end{tabular}

Note: A result is automatically shown in scientific notation if its magnitude cannot be displayed in the selected number of digits.

Exponential Format Mode

By default, Exponential Format = NORMAL. You can use MODE to select from three settings.

Note: In the history area, a number in an entry is displayed in SCIENTIFIC if its absolute value is less than .001.

\begin{tabular}{lll} \hline Setting & Example & Description \ \hline NORMAL & 12345.6 & If a result cannot be displayed in the \ & & number of digits specified by the \ & & Display Digits mode, the \ & & TI-89 / TI-92 Plus switches from \ & & NORMAL to SCIENTIFIC for that \ & & result only. \ SCIENTIFIC & 1.23456E 4 & 1.23456 × 10^4 \ & & Exponent (power of 10). \ & & Always 1 digit to the left of the \ & & decimal point. \ ENGINEERING & 12.3456E 3 & 12.3456 × 10^3 \ & & Exponent is a multiple of 3. \ & & May have 1, 2, or 3 digits to the \ & & left of the decimal point. \ \hline \end{tabular}

Chapter 2: Operating the Calculator 31

Editing an Expression in the Entry Line

Knowing how to edit an entry can be a real time-saver. If you make an error while typing an expression, it’s often easier to correct the mistake than to retype the entire expression.

Removing the Highlight from the Previous Entry

After you press ENTER to evaluate an expression, the TI-89 / TI-92 Plus leaves that expression on the entry line and highlights it. To edit the expression, you must first remove the highlight; otherwise, you may clear the expression accidentally by typing over it.

To remove the highlight, move the cursor toward the side of the expression you want to edit.

① moves the cursor to the end of the expression.
① moves the cursor to the beginning.

Moving the Cursor

After removing the highlight, move the cursor to the applicable position within the expression.

Note: If you accidentally press ▽ instead of ① or ①, the cursor moves up into the history area. Press ESC or press ▽ until the cursor returns to the entry line.

Deleting a Character

Clearing the Entry Line

To clear the entry line, press:

• CLEAR if the cursor is at the beginning or end of the entry line.
  — or —
• CLEAR CLEAR if the cursor is not at the beginning or end of the entry line. The first press deletes all characters to the right of the cursor, and the second clears the entry line.

32 Chapter 2: Operating the Calculator

Inserting or Overtyping a Character

Tip: Look at the cursor to see if you’re in insert or overtype mode.

The TI-89 / TI-92 Plus has both an insert and an overtype mode. By default, the TI-89 / TI-92 Plus is in the insert mode. To toggle between the insert and overtype modes, press [2nd] [INS].

Replacing or Deleting Multiple Characters

First, highlight the applicable characters. Then, replace or delete all the highlighted characters.

Tip: When you highlight characters to replace, remember that some function keys automatically add an open parenthesis.

Chapter 2: Operating the Calculator 33