Question about Texas Instruments TI-89 Calculator

# Ti-89 gives error of "Undefined Variable"

For example, it will not let me graph equations such as y=x and y=3x+3. Anything with a variable does not work.

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• khaos474 Aug 21, 2008

it won't let me do simple functions involving variables, as long as i place an x or y in an equation it says that undefined variable error

• ESTiiLOPii Nov 02, 2008

im trying to graph the function sinx/x and i get an "undefined variable" message.. what do i do?

• jennwhite06 Mar 21, 2009

i tried to reset my calculator to the default settings and that didn't change anything. i stil got the same error message about the undefined variable.  its only when i try to graph in 3 dimensions, not just 2.  and i tried to do define x and it gave me a syntax error

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• Contributor

You have to reset
• Press [2nd] [6] (MEM) [F1] [ENTER(RAM)]
• Select 1:ALL RAM
• Press [ENTER]
• Press [ENTER]
NOTE- erased half of my programs(I think only the ones in the main directory)

Posted on Sep 05, 2009

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I tried the reseting solution and got the syntax error, until it was pointed out to me that TI-89s, unlike the others in the series, do not automatically assume that you are multiplying, so you need to have a symbol(+,-,*,/) in between each different number or it will assume that it is a single variable(ex. 2x won't work, you need 2*x, also 2(X+1) won't work, you need 2*(x+1)) hope this helps!

Posted on Feb 09, 2010

• Bosco Nov 05, 2013

• Kawthar Harb Jan 17, 2016

thank youu , it was very helpful

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Go into home. then click F6, or the cleanup button. this should present the option 'clear a-z' click it and all your variables become variables again. :) enjoy

Posted on Sep 28, 2010

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Goto home and type Define x

Posted on Jul 09, 2008

You have to reset the variable memory, taken from the TI website
• Press [2nd] [6] (MEM) [F1] [ENTER]
• Select 2:Default
• Press [ENTER] and Defaults Set is displayed
• Press [ENTER]
good luck

Posted on Nov 04, 2008

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I go w/ the second solution of eygohlolz. Go to the main folder and delete the varible x & y or y1 and y2 then you should be ok

Posted on Sep 05, 2009

Hi,
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Posted on Jan 02, 2017

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## Related Questions:

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You referenced a variable that is not currently defined. For example, you referenced a stat variable when there is no current calculation because a list has been edited, or you referenced a variable when the variable is not valid for the current calculation, such as a after Med-Med.

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### I am trying to graph any possible equation and I get undefiend varialbe for any kind of equation as simple as x=7. It will always show as undefiend varialbe for any equation. I don't know why it does this.

Undefined variable error message displays when you evaluate a user-defined
function or run a user-defined program that references a local variable that is not
initialized (assigned a value). You have to type LineVert 7 and then graph function x=7. See captured image

May 02, 2011 | Texas Instruments TI-89 Calculator

### How do i solve an equation like 8(3x-5)-4=4x-10 where i have something on both sides of the = sign on a TI 82?

The easiest solution would be to move the variable to only one side. This is not that difficult. For example your given equation is 8(3x-5)-4=4x-10; subtracting both sides of this equation by 4x would give 8(3x-5)-4-4x=10.

Jun 28, 2010 | Texas Instruments TI-82 Calculator

### Just bought this Ti-89 and I can't graph a Diff Eq. I followed the directions from the manual on page 69 and get an error: undefined variable

Even though implied multiplication is accepted generally by the calculator when it involves a number and variable, it leads to errors when it involves two sybmols,
xsin(x) is interpreted as a function called XSIN not X*SIN(X).
Suppose you have a function y1, function of t and you write ty1 the calculator will generate an undefined variable error: It reads ty1 as a variable.To prevent the error message you should write t*y1, showing the multiplication explicitly.
Similarly if you write y1'=0.001y1(100-t) the expression y1(100-t) is interpreted as a function call: the function y1 is called with argument 100-t. If it is what you want you should explicitly express the multiplication and wrtite y1'=0.001y1*(100-t).

Feb 01, 2010 | Texas Instruments TI-89 Calculator

### I keep getting undefined variable error when i try to graph

Hello,
The default variable for the integral is x. If you have a product between two litteral symbols the * must be inserted. Arguments of functions must be enclosed between parentheses. To avoid errors clear the variables before the integration: [2nd][F6:Clean Up] [2:NewProb][ENTER]ENTER]

Hope it helps.

Sep 30, 2009 | Texas Instruments TI-89 Calculator

### I cannot plot graph in my Ti 89 graphing calculator

That means one (or more) of the variables you have in your function is not defined. Check to make sure you didn't misspell any variable name. Also, check to make sure you didn't run two variable names together. "ab" is the variable ab, not a times b.

Mar 19, 2009 | Texas Instruments TI-84 Plus Calculator

### How to graph linear equation in two variables

I am not quite sure what you are asking...

(1) if asking for graphing y= -2/3x+2, then press [diamond] [F1: Y=] type in .2/3x +2, see graph by [diamond][graph]

(2) if asking for graphing y= -2/3x+a, where a=3x, then first archive a=3x in Home screen by [home], type 3x [sto] a, then go back to y= menu, and type -2/3x+a in Y1

(3) if asking for graphing an equation that is dependent on 2 variables at the same time, use x-y-z axis (aka, change mode to graphing 3-D by [mode]graph [5:3D]) then enter desired equation in y= menu using Z function in terms of x and y aka z(x,y)= ...)

May 18, 2008 | Texas Instruments TI-89 Calculator

I have a TI-89 Titanium and I have experienced the same problem. HERE IS HOW TO FIX IT:

Goto " MODE " and scroll down the options until you get to
" COMPLEX FORMAT " change that option to " RECTANGULAR " and press ENTER until you exit out of the " MODE " screen. (very important that you press ' enter ' until you exit because if you don't, it will not save your changes. )

Sep 19, 2007 | Texas Instruments TI-89 Calculator

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