Question about Texas Instruments TI-89 Calculator

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Can't chang the logbase

I looked in the instructional book that came on the calculator and it said to type on the problem and then select logbase and put in the base number. However, whenever I attempted it, I got syntax eror. If you could give me a step by step instructional I would much appreciate it!

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  • Space Ace Nov 12, 2008

    Here is an example of a problem I have to solve. Logbase 3 X 9^logbase3^27



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  • 81 Answers

It's 2*3=6 but about the base, you can't change it in the calculators the default base it's 10 so log x it's Logbase 10^x here some logs:

log x base y = log x / log y
log (x*y) = log x + log y
log (x/y) = log x - log y
in your example log 9 base 3 = log 9 / log 3 etc.
hope you get it, and it was helpful

Posted on Jul 06, 2009


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1 Answer

How do I put in log to base 4 of x

That depends on the make and model of the calculator. A few calculators have a logBASE or similar function which takes an arbitrary base. Most only have logs to base e (ln) and base 10 (log).

However, the log of x to any base can be calculated on any calculator with logs as either
log x / log base
ln x / ln base

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How do i get my alpha key work

The TI-84 is a bit of a pain this way. You need to access the logBASE function either through the catalog or the MATH menu. You can't spell the function name as with some other calculators.

Press MATH, scroll down to the logBASE entry, then press ENTER. This will put "logBASE(" into the entry line. You can then enter the arguments and press ENTER to calculate the result. For example, to calculate the log base 2 of 8, press MATH, down-arrow a number of times to logBASE, press ENTER 8 , 2 ENTER. This should give you 3.

Apr 02, 2014 | Texas Instruments TI-84 Plus Calculator

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Subscript for log

To calculate logarithms to a base other than e or 10, use the logBASE function in the MATH MATH menu. Press the MATH key, then scroll up/down to logBASE.

Dec 12, 2013 | Texas Instruments TI-84 Plus Calculator

1 Answer

How to find a log of a different base

Use the logBASE function available in the MATH menu. Press MATH, use cursor-left/right to select the MATH submenu, then use cursor-up/down to access logBASE.

Nov 21, 2013 | Texas Instruments TI-83 Plus Calculator

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Log base while graphing

Enter the base as the second argument, following a comma. For your example, enter it as logBASE(X,2) .

May 16, 2013 | Texas Instruments TI-84 Plus Calculator

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TI-84 Calculator Gives Me the Wrong Logarithm Solution

"log(2)8" means "common logarithm of 2 multiplied by 8".

The TI-84 has three different logarithm functions.
log is the common (base-10) logarithm.
ln is the natural (base-e) logarithm.
logBASE lets you take the logarithm to any positive base.

If you want the log base 2 of 8, you want logBASE(2,8). You'll find the logBASE function in the catalog, accessible by pressing 2ND [CATALOG] ). CATALOG is the shifted function of the 0 key, the ) gets you to the Ls in the catalog.

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1 Answer

Math functions aren't working

The new OS's (2.53 MP and higher) have the MathPrint feature. However the new feature coexists with the old one CLASSIC and you can choose one or the other.
To set that up, Press the MODE key, scroll down to go to the second page. At the top you have MathPrint and CLASSIC. Use right Arrow to highlight one othe the other then press ENTER to validate. Press [2nd][MODE] to (QUIT).

If you are in MathPrint mode, the logbase command will echo as a template with squares to fill. You enter the base in the lower square and the argument in the upper one.

If you are in CLASSIC Mode logbase appears as logBASE(. Complete the argument list by entering the number whose LOG you want separated by a comma from the base)
Example logBase(8,2) yields the value 3.

Jan 09, 2012 | Texas Instruments TI-84 Plus Calculator

1 Answer

What are the keystrokes to input logarithmic functions? log(base 4) 1/4 = the answer I am looking for How would one, if possible input this equation?

You press [alpha] then [f3] to open the func menu. Use the arrow keys to highlight logbase( and press enter.
then type in the value , base). Keystrokes would be [alpha] [f3] arrow and select logbase( , then [1] [(divide)
[4] [,] [4] [)] [=] . (your screen should look like logbase(1/4 , 4) = -1.

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How do i calculate the log to a specific Base?

If you have the latest version of the firmware (2.53) you can use the logBASE function available in the CATALOG. If you don't have the latest firmware, you can get it from

Regardless of the firmware version, you can always compute the logarithm to any base by using the relationship

logb(x) = log(x)/log(b) = ln(x)/ln(b)

May 02, 2010 | Texas Instruments TI-83 Plus Calculator

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Instruction book for this calculator is shocking for sure. It would take too long to explain fully, here is an example of plotting a simple Y= graph.

In main menu, when you first turn it on, press 1
This is normal calculator mode.
Press [shift] [menu] to get the set up parameters.
Scroll curser down one to Func Type, and select Y= if this is not already set, by pressing F1
Continue scrolling down to set Coord, Grid, Axes and Label functions. Turn these on or off as desired. Turn them all off for this example. F1 and F2 select On or Off here.
Press [exit]
Press [shift] F3 to access the V-window parameters. Here you set the size of the axis in the graph
Enter 0 for Xmin, 360 for Xmax, 0.1 for scale
Enter -1 for Ymin, 1 for Ymax, and 0.1 for scale
Press [exit]
Press [shift] F4 to enter graph plot mode (Sketch mode)
Press F1 then [EXE] to clear any previous graphs
Press F5 then F1 to select Y= type graph
Display should show Graph Y=
press [sin] [ X,0,T] (this key just under red alpha key) then [EXE]
Calculator should draw a sine wave, showing 1 complete wave
Try setting the parameters in Set up, Axes On, Label On etc to see the effect.
Hope this helps a little. Page 123 in book deals with graphing.

Mar 28, 2009 | Casio FX-9750GPlus Calculator

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