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Posted on May 03, 2008
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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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  • Posted on Sep 05, 2009
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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)

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  • Posted on Feb 09, 2010
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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!

  • Bosco
    Bosco Nov 05, 2013

    Thank you! Your post was very helpful!

  • Kawthar Harb
    Kawthar Harb Jan 17, 2016

    thank youu , it was very helpful

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  • Posted on Sep 28, 2010
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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

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  • Posted on Jul 09, 2008
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Goto home and type Define x

A

Anonymous

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

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  • Posted on Sep 05, 2009
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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

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