Question about Texas Instruments TI-84 Plus Calculator

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How do i use the inverse log operation on the TI-84


I'm trying to calculate something for chemistry and the function I need to perform is the inverse log operation. To calculate the ph of a substance the formula is -log(value) but to calculate what i need to now I need to use an inverse log function and removing the - sign before the log key is not working. I have also tried the L1 function and it doesn't work either.


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  • Anonymous Mar 08, 2009

    Where is the inverse log key?

  • 10cmluko Apr 14, 2009

    With the TI-84 plus this the log key and 10x key are the same but they don't give you the same answers. For example to find the pH of x=8.9e-4 I use -log(x) and get a pH of 3.05 however when I 3.05 to 10^x I do not get the original 8.9e-4 value but instead1122.01. This is a real issue!!!

  • Anonymous Apr 27, 2009




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The problem is simple. You're trying to get an [H+] concentration which is obviously going to have a value of some number times ten raised to a negative power. Therefore, you have to insert the negative value of the pH into the 10^(x). When you insert said negative number you will come out with the right answer.
The pH of a sample of human blood was calculated to be 7.41. What is the [H+] concentration of the blood?
10^(-7.41) = [H+]
[H+] = 3.9 E-8  
(the answer should only have two sig. figs because the pH has two digits after the decimal.

Posted on May 18, 2009

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Okay, I've finally got this. Haha I've spent an hour messing around with my calculator & I'm pretty sure I know the answer.

If you have a TI-84, Press the 2ND button and the LOG button after (this will give you a small 10^( on the screen) and insert the ion concentration (for chem). You should get the answer that way.

So it would look like this:

Posted on May 07, 2009

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If I understand you correctly, the inverse of the log operation is exponentiation. So if your log = x, the inverse is 10 raised to the x power. On most TI calculators this is on the same key as the log function.


Posted on Jun 13, 2008

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Dude it's simple.
given something like [h30]=1.5x10^-3

- button, log button, 1.5 then shift button, log button (to get the 10x) then, the - button (if your integer is negative, then 3 then two parentheses.

so it looks like this:
-LOG(1.5 10^(-3))
answer should be 2.82 if not then you did something wrong.

Posted on Dec 07, 2009

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Try this: (log(V)^(-1), and if that don't work, I'm stumped. :(

Posted on May 07, 2009

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Posted on Nov 07, 2011

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How do i get inv on my TI-84 Plus caculator

To get the inverse trigonometric functions press the 2nd key then the trig function key. If you'll look at the key legends above the SIN, COS, and TAN keys you'll see the standard math notations for their inverse function.

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Im pressing the buttom that everyone is saying is the inverse key but it is saying error. i really need help with this.

It is much more enlightning to tell us what you want to do rather than talk about something that does not exist. And one thing that does not mean anything is that ellusive INVERSE key that everyone and his dog is looking for.
The additive inverse of a number a is its opposite (-a). The key to use is the change key (-).
The multiplicative inverse of non-zero number a is its reciprocal 1/a
The inverse of the natural log (LN) function is the EXPONENTIAL function e^(x). On most calculators if one function is accessed diectly (the marking is on the key), its inverse is accessed by pressing [SHIF] (Casio, or [2nd] (TI) or [2ndF] (Sharp).
The inverse of the function raise 10 to a power [10^x] is [LOG]
Similarly, the inverse of the sine function SIN is the arcsine [sin^-1]. To access the latter, it you press [2nd][SIN]. The same is true for arcosine [2nd][COS], and arctangent [2nd][TAN]

The inverse of the square functions [x^2] is the square root function [2nd][x^2]
Inverse of x^3 is cubic root
This is just a quick overview.

Feb 16, 2012 | Texas Instruments TI-84 Plus Silver...

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Hi, how do i calculate log^-1(-2) on my ti-30xa? thank u.

The inverse of the log function is the power function.
For log in base 10 that inverse is 10 to a power of
More generally, let b be the base of the logarithm. If y=log_b (x) then x=b^y
For your case log=log_10, to calculate the inverse you perform 10^(-2)=0.01=1/100
On calculators the log in base 10 and its inverse share the same physical key. One is accessed directly, the other is the shifted key function.

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How to take anti log in casio fx 991 ms and give example?

Depending on the actual log function you are talking about, the inverse function (what you call the anti log) can be one of several things.
The inverse of the natural log (LN) is the exponential function e^x.
If y= ln(x) then x=e^y
On a calculator functions that are inverse of one another share the same physical key. If one function is marked on a key, the inverse function is usually the SHIFTED (or 2nd) key
The inverse of the common (decimal logarithm) is the power function with 10 as base.
Example: if y= log(x) then x=10^y
For an arbitrary base (must be positive) if y= log_b(x) then x=b^y.
Note: I do not think that the FX-300ms can perform log calculations in bases other than e (natural log) or 10 (common decimal log).

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How do I calculate inverse log on this calculator? Let's use -pH=-7.41

To get the concentration C of hydronium ions use the relation
C=10^ (-pH)=10^ (-7.41)=3.89045*10^(-08) or just C=3.89*10^(-8) mol / L
The inverse of the function log in base 10 is 10 to the power of.

pH=-log(C) and C=10^(-pH)

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What button do you push on the TI-86 calculator to do the inv log function?

For the inverse natural log, press 2nd LN. For the inverse common log, press 2nd LOG.

For example, to calculate the inverse natural log of 2, press 2nd LN 2 ENTER and you'll get about 7.389 .

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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.)

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1 Answer

I am trying to get the inverse log from 1x10-4.62

I suggest you reformulate the question. If you are doing pH questions, give the pH and we will show you how to get the concentration. Alternatively, give the concentration and we will show you how to obtain the pH. Keep in mind that in the context of pH questions, pH is restricred to the interval [0,14], and that imposes restrictions on the possible values of the concentration.

If c=concentartion, then
This is equivalent to

Assuming that this is what you want to do (ie. calculate the concentration)
Press [2nd][log] to access the 10^ function
Screen displays 10^(
Enter the change sign [+/-]
Enter the pH value 4.62
Screen displays 10^( -4.62)
Press [=]
The result is 2.398832919E-05. To 3 significant digits the concentartion is c=2.39E-05 mol/L of H+/H3O+ ion

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How do I key in log and inverse log at the same time?

There are very few instances where you have two press two keys AT THE SAME TIME, the most notable of them is when you want to force the calculator into the BOOT SCREEN. Most key combinations are key sequences, meaning you press a key and THEN press another.

This said, let us get back to your question.

When you apply a function on an expression, then apply the inverse of the function on the result you get the original expression back.
If f is a function and f^-1 its inverse, by definition f^-1[f(x)]=f[f^-1(x)] =x
As you can see you do not need a calculator to find the result.

Concerning the logarithmic functions

For the natural logarithms (logarithms in base e) labeled [ln], the inverse of the logarithm is the exponential function e^
ln[e^(x)] =e^[ln(x)] =x

For the common logarithms (logarithms in base 10), labeled [log], the inverse function of the log is the raising 10 to the power of. It is usually called the antilogarithm or antilog.

y= log(x) is equivalent to x=10^(y)

Try the following exemple

log(14) = 1.146128036
10^(1.146128036) =14

To access the 10^x function you press [2nd][LOG]
To access the exponential function you press [2nd][LN]

Jan 06, 2010 | Texas Instruments TI-84 Plus Calculator

1 Answer

How do i enter pH on a TI 30 calculator

This post answers two questions
  1. How to obtain the concentration knowing the pH?
  2. How to obtain the pH knowing the concentration
If you are not interested in the theory, jump to the examples at the end of the post.

As you well know the pH is the negative of the log in base 10 of the H+/H3O+ ion concentration. If we use [H+] to represent that concentration, then pH=-log[H+].
To obtain the [H+] you need to calculate the antilog. You write the definition in the form log[H+] =-pH and then calculate 10 to the power of each member. The equality remains valid as both members are treated similarly. Thus
10^( log[H+] ) = 10^(-pH)
Since raising 10 to a power is the inverse function of taking the log in base 10, 10^(log(x))=log(10^(x)) = x (they are inverse of one another), you are left with


Your calculator has a function [10 to x] accessed by pressing the [2nd] function key. To use it you must enter the negative value of the pH, press the [2nd] function key then the [10 to x], then the = key to get the result (concentration)

1. Let the pH=5.5, what is the H+ concentration?

With [(-)] being the change sign key, then
[H+]:[ (-) ] 5.5 [2nd][10 to x] [=]
The result is 0.000003162 or 3.16 x 10^(-6)

Calculating the pH

For all H+/H3O+ concentrations of the form 1.*10^(a) where a is an integer number between 0 and -14, the pH is the negative value of the exponent.
Concentration =10^(-3), pH=3
Concentration=10^(-11), pH=11

For other concentrations such as 3.567*10^(-8), one cannot use the shortcut above, but have to calculate the log of the concentration

[H+/H3O+] = 3.567*10^(-8)
pH= - log(3.567*10^(-8))
This is keyed in as follows (to minimize the number of parentheses)

8 (-) [2nd][10 to x] [*] 3.567 [LOG] [=] (-)
Here you have two (-) change sign, the first is entered after the exponent of 10, the other at the end of the calculation to take the negative of the displayed result. You may notice that it is entered in the reverse order of the defining relation - log(3.567*10^(-8)).
To verify your calculation, the result is 7.447696891 or just 7.45
If you have a problem with the first (-) try entering it before you type in 8.

Hope it helps and thank you for using FixYa
And please, show your appreciation by rating the solution.

Dec 07, 2009 | Texas Instruments TI-30XA Calculator

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