Isn't it funny how much busier this site gets around exam times...

So, as for my last minute, panic-fuelled question.

When do you know when to use log to the base 10 and log to the base e?

I was working through the maths4scotland logs pp (a question where an exponential decay function intersects with a line to be exact) and I used log to the base e. However, they used log to the base 10 and so we had different answers.

So how can I tell when to use which, and is this a funndamental error, or would I have gained any marks for my otherwise correct method of working?

Any help on this matter would be great,

campbellk2

**1**

# Logs

Started by campbellk2, May 18 2008 02:30 PM

6 replies to this topic

### #1

Posted 18 May 2008 - 02:30 PM

### #2

Posted 18 May 2008 - 02:37 PM

generally you use the base, that is most appropriate to the question, ie, if there is an e in the question you use to base e, etc. but otherwise it is up to you, so I don't think it would matter, (though i think any marker would be annoyed if you decided to use base 47.265...)

If you could post the question I may be able to give you a more specific answer.

Hope this helps

If you could post the question I may be able to give you a more specific answer.

Hope this helps

**=-=-=Marcus=-=-=**### #3

Posted 18 May 2008 - 02:43 PM

Hi,

Here is a link to the question. http://www.maths4scotland.co.uk/Higher%20Powerpoint.htm

It is the logs powerpoint and the question is on slide number 27. Sorry that I couldn't just post the question, but I couldn't copy the slide.

Thanks for your help!

Here is a link to the question. http://www.maths4scotland.co.uk/Higher%20Powerpoint.htm

It is the logs powerpoint and the question is on slide number 27. Sorry that I couldn't just post the question, but I couldn't copy the slide.

Thanks for your help!

### #4

Posted 18 May 2008 - 03:29 PM

yeah the question there, would be a prime example of when it doesn't matter which base you use, and i doubt you would of lost marks for using e instead of 10, as it didn't specify...

You should have still got the same final answer though...3.402

You should have still got the same final answer though...3.402

**=-=-=Marcus=-=-=**### #5

Posted 18 May 2008 - 03:31 PM

Thanks,

I guess I must have went wrong somwhere...I'll try it again.

Thanks for clearing things up,

campbellk2

I guess I must have went wrong somwhere...I'll try it again.

Thanks for clearing things up,

campbellk2

### #6

Posted 18 May 2008 - 05:22 PM

I need a couple of things cleared up:

is 10^x the inverse of log(base10)x ?

is e^x the inverse of ln?

Is log(baseE) the same as ln?

is 10^x the inverse of log(base10)x ?

is e^x the inverse of ln?

Is log(baseE) the same as ln?

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