# log Function on Calculator

1. I have a basic scientific calculator....such as not a TI graphic calculator.

I saw in my Algebra book that we will have to work with log.

It says that 3^2 (3 squared) = 9 and if I were to do the log function for this it would be 3 log 9, and should = 2.

Well, when I put in 3 log 9 on my calculator, the answer is 2.8627.......

I thought maybe I should just not round up, but when I tried the 5 log 25 for 5^2 (5 squared), the 5 log 25 = 6.9897.........

So, obviously, my theory of not rounding up isn't correct because the answer would have needed to be 5 point something and not 6.9.

SOOOOOOOO, how do you use the log function on a calculator? :uhoh21:

Thanks to anyone that can help!
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2. ### About Fun2, RN, BSN

Joined: Dec '04; Posts: 9,618; Likes: 364
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3. Girl, I am studying for my algebra final right now and I say lets dump the math and go get drunk!!!!!!

Quote from Fun2Care
I have a basic scientific calculator....such as not a TI graphic calculator.

I saw in my Algebra book that we will have to work with log.

It says that 3^2 (3 squared) = 9 and if I were to do the log function for this it would be 3 log 9, and should = 2.

Well, when I put in 3 log 9 on my calculator, the answer is 2.8627.......

I thought maybe I should just not round up, but when I tried the 5 log 25 for 5^2 (5 squared), the 5 log 25 = 6.9897.........

So, obviously, my theory of not rounding up isn't correct because the answer would have needed to be 5 point something and not 6.9.

SOOOOOOOO, how do you use the log function on a calculator? :uhoh21:

Thanks to anyone that can help!
4. That happens because most likely your calculator doesn't have a general logarithm function (especially if it's a basic scientific calculator.)

Most scientific calculators have two symbols: LOG and LN. LOG is the base-10 logarithm, while LN is the base-e logarithm. (e is 2.7182...) Try entering LOG 10 in your calculator and hit ENTER on it, the result should be 1.

What you typed in: 3 LOG 9 is 3*(base-10 LOG 9), which is really 2.86... If you try 3 LOG 100, you'll get 6. (Because you raise 10^2 and then multiply by 3.)

As far as I know, even most advanced scientific calculators don't have a general logarithm function (I have a TI-68, non-graphing one; I used it through my algebra class and it was enough - this one, too, has only log and ln.)
5. I like txspadequeen's idea! :biere: (Good luck to you!!!! I hope things have been going well for you at the new college!)

LKG6, mine has log and the next button to it is In (or at least it looks like an I instead of L....more like ln.) :chuckle

Anyway..... I did the log 10, and it did come up as 1.

*******
After reading this post, I started looking through the book again, and found where it gave the steps to find the log on the calculator.

Thanks for explaining that I was doing it wrong!!! lol

Quote from LKG6
That happens because most likely your calculator doesn't have a general logarithm function (especially if it's a basic scientific calculator.)

Most scientific calculators have two symbols: LOG and LN. LOG is the base-10 logarithm, while LN is the base-e logarithm. (e is 2.7182...) Try entering LOG 10 in your calculator and hit ENTER on it, the result should be 1.

What you typed in: 3 LOG 9 is 3*(base-10 LOG 9), which is really 2.86... If you try 3 LOG 100, you'll get 6. (Because you raise 10^2 and then multiply by 3.)

As far as I know, even most advanced scientific calculators don't have a general logarithm function (I have a TI-68, non-graphing one; I used it through my algebra class and it was enough - this one, too, has only log and ln.)
6. Logarithms are the inverse functions of exponents. When you press 3 and then the LOG key, the answer you get is not going to be 9. The answer you get is actually the power on the number 10 that will give you the number 3. Thus, this is the inverse function. That is very different from squaring and number and taking it's square root. Anytime you want to use the LOG key you only have to input a number and press the LOG key. Again, the answer you get is actually the exponent that would be applied to the number 10 to get the number that you input into the calculator. If you are squaring numbers or finding the square root of a number you should use the keys for that purpose. There are also two other keys for finding powers greater than 2 and to find roots higher than 2. The LOG and LN keys are not used for what you are trying to do. Logarithms are algebraic functions that are introduced at the end of Intermediate Algebra and used in calculating things like compounded interest.
7. Quote from Fun2Care
I have a basic scientific calculator....such as not a TI graphic calculator.

I saw in my Algebra book that we will have to work with log.

It says that 3^2 (3 squared) = 9 and if I were to do the log function for this it would be 3 log 9, and should = 2.

Well, when I put in 3 log 9 on my calculator, the answer is 2.8627.......

I thought maybe I should just not round up, but when I tried the 5 log 25 for 5^2 (5 squared), the 5 log 25 = 6.9897.........

So, obviously, my theory of not rounding up isn't correct because the answer would have needed to be 5 point something and not 6.9.

SOOOOOOOO, how do you use the log function on a calculator? :uhoh21:

Thanks to anyone that can help!
Did your calculator come with a booklet? Or can you get one from the manufacturor? Maybe dowload it? Usually it will tell you there.

My calculator came with one, and I never even read it because I found out too soon that calculators were not permitted in my Algebra class (insert scream here).

Good luck in the class
Last edit by Jessy_RN on Dec 12, '05
8. Jess, I would have taken my Algebra with a different instructor! I've never had an Algebra class that calculators weren't allowed....except maybe in high school. That's too long ago...LOL (Also, I've had this calculator a while, I used it on my last Algebra class, so I have no idea where the booklet is.)

Daytonite, ty for your response. I had Algebra in 2001, you'd think I would remember doing logs. Oh well.

I think I'll be fine now, although in my book the directions for using the calculator is all backwards! It says enter the number first, I have to enter log first. It says enter the number first I have to enter shift then 10x first.

I'll be fine when I get to that point, or I'll be asking more questions. LOL

Quote from Future_RN_Jess
Did your calculator come with a booklet? Or can you get one from the manufacturor? Maybe dowload it? Usually it will tell you there.

My calculator came with one, and I never even read it because I found out too soon that calculators were not permitted in my Algebra class (insert scream here).

Good luck in the class
9. Actually, I don't remember doing anything with logs in high school until I was in Trigonometry. We had to do them by our own calculations using a table at the back of the book because slide rules were still being used at that time! They've only introduced the subject of logarithms in the second to last chapter of my Intermediate Algebra book. Formulas for circles, ellipses and hyperbolas were in the last chapter. The very same level of information on logarithms is in my college level Trig textbook and it is in the last chapter as well. I'm telling you, don't sweat the logarithm thing. It's not something that is used a lot in plain old algebra.
10. Yeah, what's up with that??

I don't remember finding the radius and center points of a circle, or sides of a triangle either. I mean, it's not a big deal b/c both of them are extremely easy, but I don't remember learning all of this stuff when I took it before.

I don't understand why all of this geometry stuff is in Algebra, or as you said, the trig stuff in algebra.

Oh well, I gotta act like a big girl and get through this, geometry....no no, trig.....no no Algebra.

My class starts tomorrow!

Quote from Daytonite
Actually, I don't remember doing anything with logs in high school until I was in Trigonometry. We had to do them by our own calculations using a table at the back of the book because slide rules were still being used at that time! They've only introduced the subject of logarithms in the second to last chapter of my Intermediate Algebra book. Formulas for circles, ellipses and hyperbolas were in the last chapter. The very same level of information on logarithms is in my college level Trig textbook and it is in the last chapter as well. I'm telling you, don't sweat the logarithm thing. It's not something that is used a lot in plain old algebra.