Question about Texas Instruments TI-89 Calculator

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How to use ti-89

How do you store a number, say like the point of intersection as A, B, C, D...
and every time when i type in xsin(x^2), the calculator tells me it's undefined variables. and when i try to integrate it on the home screen, the calculator can't process the function either.

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The calculator is very sophisticated but it does not solve all problems. In particular it does not know (does not have) the Integration by parts algorithm. But you can always have a numerical value of a definite integral.

To store a number in any variable
You enter the number 18[STO->][Alpha]A stores 18 in A.

My opinion is that you cannot take advantage of the functionalities of this calculator if you do not take some time to consult the manual. You do not have to read the whole thing, just read the chapter or the exemples that show you how to handle your current question (whatever it may be.)

Hope it helps.

Posted on Sep 12, 2009


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Find all stationary points of y=(x-2)^4

There is no points of inflection for this function. See cap images below.



Oct 17, 2013 | Texas Instruments TI-89 Calculator

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I have 2 equations programmed, and want to find the points of intersection. I can see them, but not sure how to find the exact values of intersection. Can you help?

click the trace button to see exact values on a function. When in trace mode you can type in x values and see exact y values.

Sep 11, 2011 | Texas Instruments TI-89 Calculator

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Solve() gives me wrong answer. -20^2=12^2+2X(-5-3). The answer is -16, But my TI-89 is giving me 34 during the solve funtion. my TI-83 is also giving me -20^2=-400 not 400.

Enter the first term as (-20^2), not as -20^2. Without the parentheses the calculator interprets it as
-(20^2), which is not what you want.

Also, make sure you use the (-) key just to the right of the decimal point and not the - key.

Aug 31, 2011 | Texas Instruments TI-89 Calculator

1 Answer

When i try to graph a function the calulator shows "undefined variable" what should i do?

When you are entering the expression, do not use implied multiplication. For example if your expression contains x times sin(X), enter it as X*SIN(X), otherwise the calculator will look for a function XSIN and will not find it, giving you the error message. No need to enter the explicit multiplication sign if you have a number to the left of the function. Also be wary of entering X3 for 3 times X.

Apr 13, 2011 | Texas Instruments TI-89 Calculator

1 Answer

Difficulties with producing a Residual plot.

In your calculations you are using a variable which stores a numerical value. In the HOME screen, on the command line use the keyboard to type in NewProb (case sensitive) and press ENTER. It will rest the variable to their default state.

If you are using a product of two functions, exeample x times sine of x, you must explicitely insert the multiplication sign otherwise the calculator will interpret the group xsin(x) as some unindentified entity.
If you have expressions such as 3*x you must not write them with the number to the right in the form x3. It will be interpreted as an undefined entity.

To avoid problems of interpretations always insert the multiplication sign.

Mar 02, 2010 | Texas Instruments TI-89 Calculator

2 Answers

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

3 Answers

Argument error whenever I type equations with variables.

Perhaps you have some data stored in the x variable.

With the calculator on, press [2nd] then the minus button. This brings up a list of all the saved data in the calculator. Look through the far left column of the list for x.

If you find x in the list, highlight x, then press F1, and then select delete.

Now it should work like normal.

Oct 22, 2009 | Texas Instruments TI-89 Calculator

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Different answer fro my TI-89 AND MY tI-81

Your TI81 can only perform numerical calculation: It always give uour numbers. The TI89, a more sophisticated calculator, can of course do numerical calculation, BUT ALSO symbolic ones. You ask it for the derivative of sin(x) and it will give you cos(x).
Anyway, if you want a decimal result for you calculation above one of the numbers must have a decimal point (instead of writing 2PI write 2.PI.

The TI 89 can do exact calculations. But if you want approximate results any number in the sequence of operations must have the mark of a decimal. Numbers without decimal marks are considered integers, Integer numbers with a decimal mark are treated as floating point numbers ( meaning decimal).

Hope it clarifies things for you.

Nov 15, 2008 | Texas Instruments TI-89 Calculator

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My TI-89 cant do simple calculations.

You have to set how the calculator handles numbers. To do this follow these steps: 1. Press the 'MODE' button. This brings up the calculator's main settings page. 2. Scroll down until you reach a field titled 'Exact/Approx...'. This is the setting for how the calculator handles numbers, whether it will show the exact answer (which is usually in fraction format) or whether it will show an approximate number (which will be in decimal format). 3. Press the right arrow which will bring up the options for that setting. You must now choose between three ways of handling numbers: -'1:AUTO' will determine which type of answer the calculator will give based on what numbers you want it to calculate (e.g. if you want an answer in decimal format just add a decimal somewhere in your problem). -'2:EXACT' will automatically display all answers in either whole number format or in fraction format. -'3:APPROXIMATE' will automatically display all answers in decimal format. 4. After you have selected one of those options press enter one more time to get out of the 'MODE' dialogue and return to the 'HOME' screen. Now try a problem and see what happens. Personally I like using 'AUTO' because then I don't have to keep returning to 'MODE' when I want either or. Hope this helped, I had the same problem when I first started using the TI-89.

Sep 18, 2007 | Texas Instruments TI-89 Calculator

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