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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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
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Press LOG 3 ENTER.

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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.

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

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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.

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

The TI-84 has three different logarithm functions.
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ln is the natural (base-e) logarithm.
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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)
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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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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)

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