Three layers on one key
Every key has its main function printed on the key itself. Above it are up to two more labels: one for 2nd and one for ◆ (diamond). A letter next to the key is the alpha layer. Press the modifier first, then the key; you do not hold them together. 2nd and ◆ apply to the next key only.
x, y, z and t have their own keys because you need them so often. For other letters press alpha and the key with that letter. For a whole word, 2nd alpha locks alpha mode until you press alpha again. On the handheld, uppercase letters use the ↑ shift key.
The keys you use every day
| Function | Keys |
|---|---|
| ∫ | 2nd7 |
| d | 2nd8 |
| √ | 2nd× |
| π | 2nd^ |
| ℯˣ | ◆X |
| ln | 2ndX |
| sin | 2ndY |
| sin⁻¹ | ◆Y |
| ′ (prime) | 2nd= |
| [ and ] | 2nd,and2nd÷ |
| { and } | 2nd(and2nd) |
| ∞ | ◆CATALOG |
| ⅈ | 2ndCATALOG |
| ≈ decimal | ◆ENTER |
| ANS | 2nd(−) |
| ENTRY | 2ndENTER |
| MATH menu | 2nd5 |
| UNITS | 2nd3 |
| ▶ convert | 2ndMODE |
| ≠ | ◆= |
| ≤ and ≥ | ◆0and◆. |
| Y= / GRAPH | ◆F1and◆F3 |
| QUIT | 2ndESC |
Sine, cosine and tangent are 2nd Y, 2nd Z and 2nd T; their inverses are the ◆ versions of the same keys. ANS inserts the last answer, and ENTRY brings back the last input so you can edit it.
HOME and the toolbar menus
HOME is the screen where you type expressions and get results. Its toolbar menus sit on F1 to F6: F2 Algebra holds solve(, factor(, expand( and zeros(; F3 Calc holds d(, ∫(, limit( and Σ(; F4 has Define. F6 is 2nd F1. Inside any menu, press the number of an item or move with the arrows and press ENTER. ESC closes a menu without choosing.
| Input | Result |
|---|---|
| solve(x^2=9,x) | x=−3 or x=3 |
| factor(x^2-1) | (x−1)·(x+1) |
| expand((x+1)^2) | x2+2·x+1 |
Exact or approximate: MODE and ◆ ENTER
MODE holds the Exact/Approx setting with three choices. AUTO keeps exact input exact and gives a decimal as soon as the input contains a decimal point. EXACT always keeps fractions, roots and π. APPROXIMATE always gives decimals. In any mode, ◆ ENTER gives the decimal for one entry, like approx(. exact( goes the other way.
| Input | Result |
|---|---|
| approx(π) | 3.14159265359 |
| exact(.25) | 1/4 |
MODE is also where Angle switches between RADIAN and DEGREE. Calculus needs radians; many geometry and physics problems use degrees. A wrong angle mode is behind many wrong trig answers.
CATALOG: every command in one list
CATALOG lists all commands alphabetically. Press the key with the first letter to jump, then scroll and press ENTER. The status line shows the syntax of the highlighted command, which helps when you do not remember the order of the arguments. Commands that are not in a toolbar menu, like impDif(, are quickest from here.
Storing values with STO▶
STO▶ stores the value on its left in the variable on its right and shows as →. The variable keeps its value until you delete it with DelVar or clear all one letter variables with NewProb from the Clean Up menu (2nd F1).
| Input | Result |
|---|---|
| 5→a | 5 |
| DelVar a | Done |
| a | a |
The with operator |
The | key, left of 7, substitutes values for one entry only, without storing anything. expression|x=2 evaluates the expression at x = 2. Join several conditions with and.
| Input | Result |
|---|---|
| when(x>0,1,-1)|x=2 | 1 |
| nDeriv(x^3,x)|x=2 | 12.0 |
Common mistakes
- A stored variable. If x holds 3, solve(x^2=9,x) no longer solves for x. Run NewProb before a new problem.
- xy is not x times y. Two letters next to each other are one variable named xy. Type x*y.
- x(x+1) is a function call. A letter before a parenthesis is read as a function. Type x*(x+1).
- Minus or negative. Use (−) for a negative number. Starting a line with the minus key subtracts from the last answer.
- Wrong angle mode. Check RADIAN or DEGREE in MODE before trig work.
- A missing parenthesis or argument. Most commands need the variable as an argument: solve(x^2=9,x), not solve(x^2=9).
FAQ
What does the ◆ key do on the TI-89 Titanium?
◆ (diamond) is the second modifier next to 2nd. It reaches the functions printed in its color above the keys, such as ≈ on ENTER, ∞ on CATALOG, Y= on F1 and GRAPH on F3.
How do I get a decimal answer instead of a fraction?
Press ◆ ENTER instead of ENTER, or set Exact/Approx to APPROXIMATE in MODE.
How do I clear all variables?
Press 2nd F1 to open the F6 Clean Up menu and choose NewProb. It clears the one letter variables and the home screen history.
Calc89 is an independent app intended for use with TI-89 Titanium. It is not affiliated with or endorsed by Texas Instruments. TI-89 Titanium is a trademark of Texas Instruments.