Hi this is Rob.
I am going to show you how to calculate Logarithms
on the TI-89 Titanium Graphing Calculator.
A quick review on logarithms.
A logarithm is a way to solve for x, when
x is an exponent.
For example, 10 to the x power equals 1000.
This 10 is called the base.
The way we write the above expression as a
logarithm is log 1000, which is equal to 3.
Thus, x equals 3 in the above expression.
Why?
Because 10 times 10 times 10 equals 1000.
In logarithms we write the base here, except
if the base is 10, then we leave this area
blank.
On the TI 89 there is no log button as there
is with other TI calculators.
To solve a base 10 logarithm on the TI-89
Titanium, press this green star button here,
and then the number 7 button here.
This log open parenthesis appears.
Enter 1000 and closed parenthesis here.
Now press the enter key.
And there is the answer to the right.
3.
Ok, what if the logarithm is not a base 10
logarithm.
For example: 2 to the x power equals 16.
In this problem the base is Base 2.
X equals 4 because 2 times 2 times 2 times
2 equals 16.
How do we calculate a logarithm on the TI
89 when the base is not base 10?.
Here is our equation with a base of 2.
And here is how we write that equation in
log notation.
Log 2 16.
Repeat the steps to get the log function to
appear.
Press this green star button here, and then
the number 7 button here.
Now we have logbase open parenthesis.
In our logarithm Log 2 16, enter the 16 first,
then a comma here, then enter the base last,
in this case it is base 2, enter 2 and enter
a closed parenthesis.
Now press the enter button.
There to the left you can see our log 16 base
2 and to the right is the answer.
4.
Sometimes when doing logarithms on this calculator
you may get an error message.
If you get an error message, you need to change
this part here to say APPROXIMATE.
Do do that, press the mode button here.
This window pops up.
Press the F2 button here.
Then use the down arrow key and go down to
here Exact/Appox.
Press the right arrow key and this window
pops up.
Choose number 3, APPROXIMATE.
Press enter.
Press enter again.
And now you can see here that it says APPROXIMATE.
OK, that is it.
That is how to calculate any base logarithms
on the TI-89 Titanium Graphing Calculator.
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