Question about Texas Instruments TI-89 Calculator

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How do I get my TI-89 calculator to give me a decimal approximation of a natural log? When I type in ln(45) I get exactly the same thing back.

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Press diamond then ENTER to convert the display the current value in numeric form.

To get everything to display this way, press MODE F2 then scroll down to Exact/Approx, press right-arrow, press up/down select APPROXIMATE, then press ENTER. Press ENTER once again to save your settings.

Posted on Sep 01, 2010

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2 Answers

Change base log

The TI 86 has two logarithmic functions: natural logarithm (ln) and common (decimal) logarithms (log). If you need the logarithm in any other base than e or 10 you need to use one of the two equivalent expressions
log_b(x) =ln(x)/ln(b) =log(x)/log(b)
Here b is the value of the base of the logarithm and x is the argument (the value whose logarithm you are seeking). Of course the argument x must be a positive number.
Note: On the TI 86 the log function can calculate the logarithm of a complex number, according to the manual.

Sep 22, 2013 | Texas Instruments TI-86 Calculator

1 Answer

TI-89 "ln" function returning a "ln" answer

To convert a result from symbolic to numeric, press diamond ENTER. To have all results appear in numeric form, press MODE F2, use down-arrow to get to the "Exact/Approx" line, press right-arrow, down-arrow to "3:APPROXIMATE", press ENTER ENTER.

Feb 07, 2013 | Texas Instruments TI-89 Calculator

1 Answer

Hi i am trying to figure decimal for natural logarithm can i do thi with a ti 89??

Yes. If the calculator is showing something like ln(2) for an answer, press diamond ENTER to convert to a numeric answer. To have all results come out numerically, press MODE F2, use down-arrow to move to Exact/Approx, right-arrow, and select APPROXIMATE. Press ENTER twice to save the change.

Oct 27, 2010 | Texas Instruments TI-89 Calculator

1 Answer

Calculator wont show decimals

To convert a single value to decimal, press Diamond then ENTER. To get them all that way, press MODE then F2. Scroll down to Exact/Approx and change it from Auto or Exact to Approximate.

May 12, 2010 | Texas Instruments TI-89 Calculator

1 Answer

Okay, so I have a problem where I need to get what 25/3 is...when I put this into my ti-89 titanium from the home screen the only answer it gives me is 25/3, what is up with that? It won't do simple...

If you leaf through the manual with its 500 some pages you will diuscover that your last statement is not quite right.
The "problem" is that the calculator is configured to perform EXACT calculation where fractions are kept as fractions and radicals as radicals.

To have your fractions displayed as decimal numbers ALL THE TIME
Press [MODE][F2]
Use Arrow down to highlight [Exact/Approx
Use right arrow to unfold the menu list and select [3:Approximate]
Press [ENTER] to save configuration

There are two other ways to convert an exact result into an approximate one
  1. If you enter 25./3 or 25/3. or 25/3. and press [ENTER] the fraction will be displayed as a decimal number (The dot is a decimal mark, and it instructs calculator to perform approximate calculations)
  2. If enter 25/3 without the decimal marks and press [Diamond][ENTER] the result will be decimal.

Feb 17, 2010 | Texas Instruments TI-89 Calculator

1 Answer

TI-89 decimal to fraction

Here is what you do:

1) Press the Mode button.
2) Scroll down the list that appears until you find "Exact/Approx".
3) Change the setting for "Exact/Approx" to Exact.
4) Press enter to save the settings change.

You have three possible settings for "Exact/Approx":
1) Auto - The calculator will try to determine the best format.
2) Exact - The calculator will always give the answer in fraction form.
3) Approximate - The calculator will always give the answer in decimal form.

Nov 15, 2009 | Texas Instruments TI-89 Calculator

1 Answer

Natural logarithm with TI-30XA calculator

I noticed that this calculator doesn't have a natural logarithm function as well. You can can always use the fact that
ln x = (log x) /log e or since log e is approximately .43429482
ln x = (log x)/.43429482. The greatest solution and it might be worth the 15 bucks or so to get a calculator with e^x and the natural logarithm function.

Feb 20, 2009 | Texas Instruments TI-30XA Calculator

2 Answers

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

2 Answers

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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