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How do i calculate the log of a number? - Texas Instruments TI-30XA Calculator

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To calculate the natural log of a number use [LN] key. You enter it as
number [LN] [=] exemple 15.32 [LN] [=] gives 2.729150164
To clculate the log base 10 (common logarithm) you use the [LOG] key
15.32 [LOG][=] gives 1.185258765.

Hope it helps

Posted on Sep 17, 2009


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How to fix error mesage on TI-30Xa. Every time I press LOG an error sign comes up. how do i fix this?

To take the log of a number, enter the number then press the LOG button, then the =. To take the log of a negative number, enter the negative number using the +/- key just to the right of the decimal point. To calculate the negative of a log, calculate the log and then negate it using +/-. To calculate the antilog (inverse logarithm), press 2nd then LOG.

Bear in mind that LOG is the common (base-10) logarithm. For the natural (base-e) logarithm, use the LN key to its right.

How do i use log functions on the HP 39g+. For instance i want to use log10 1000 which should equal 3 or 3^5=243 so log3 243 should equal 5. If i press log the calculator shows: log( If i...

To calculate the common log ( LOG base 10) of a positive number, just press the LOG key, the one above the blue Division key, then enter the number and close the right parenthesis. Press the ENTER key to get the result.

If you want to calculate the log in a base other than e (natural) or 10 (decimal) logarithms, you need to make use of one of the equivalent formulas below

log in base a of a number b
log_a(b)=log_10(b) / [ log_10(a)] or
log_a(b)= ln(b)/ln(a)

How can I calculate Log2 2.5 on my calculator.. since everytime I start entering it i start by pressing log and right away it says ERROR.. by the way the 2 right after log is suposed to be a little 2.

First of all, to compute the log of a number, enter the number first then press the LOG key.

Second, to compute the log to a base b other than e or 10, use the relationship
logb(x) = log(x) / log(b) = ln(x) / ln(b)
You can use either the common log (log) or the natural log (ln), as long as you're consistent.

So, to calculate log2(2.5), press
2 . 5 log / 2 log =
2 . 5 ln / 2 ln =

How do i perform log and log inverse or antilog calculations on my sharp EL W-535 calculator

Press the log key, enter a poistive number and press the = key.
To calculate the inverse of the decimal log use SHIFT LOG to access the function 10^x (the inverse of the log function.)

How to type log base 2

You can't. However, you can calculate the log base 2 of any number by calculating

log2(x) = log(x)/log(2) = ln(x)/ln(2)

That is, the log base 2 of any number is the log of that number divided by the log of 2.

How do I use this calculator to find the logarithm of a given number? When looking up logs in the old tables, we had to change the number into scientific notation before entering the mantissa. I'm not sure...

Use the LOG key on the top row for common logs, the LN key for natural logs. In either case, simply enter the number as given then press the appropriate log key, then press =.

How do you input -log ?

Use the log function (common logarithm). See screen capture for markings on key.
To evaluate the negative of a logarithm
Enter the number (argument) of the logarithm
Press the = key to have it calculated.
While result is still displayed, press the sign change key or (+/-).

Beware that -log(number) is not necessarily a negative value.

Another way to calculate -log is to use the relation
log(1/a)=-log(a) .


How to use the Logerithmic function on this calculator


Logarithms in base 10 :Common logarithms
  1. The calculator has a key labeled [LOG]. It allows you to calculate the common logarithms (logarithms in base 10).
  2. To calculate the common logarithm of a (positive) number you type in the number, press the [LOG] key .
  3. Ex: 15.32 [LOG][=] gives 1.1852558765
Logarithms in base e : Natural logarithms
  1. The calculator has a key labeled [LN]. It allows you to calculate the natural logarithms of positive numbers.
  2. Ex: natural log of 15.32 is entered as
  3. 15.32 [LN] gives 2.729159164
Hope it helps.
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Explain how to find the logarithm, base 18, of a number.

Sorry I clicked the post a clarification request too fast.

You cannot compute it directly. You have to use the formula

log_18(number) = ln(number)/ln(18).

Here log_18 is log in base 18, ln is the natural logarithm (naeperian or log in base e).

Alternatively, you can use

log_18(number) = log(number)/log(18)

where log is log in base 10.

If you use those types of calculations a lot, it might be a good idea to get a Casio FX-115ES, or a Casio FX-991 ES. They have other nice features like fraction calculations and radicals.

Hope it helps.
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