Hello,

I have never really understood the difference between the log and the ln function. Both are logarithmic functions. How do you know when to use which?

/Jones

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- Feb 16th 2009, 01:55 PM #1

- Feb 16th 2009, 02:23 PM #2
Anyone can start a real disagreement started with that question.

It is fair to say that historically log has referred to base 10 logarithms whereas ln has referred to base e logarithms called the natural logarithm. However, some mathematicians have of late suggested that we use log for all logarithms and use the base e as the normal base. Notably, that is the position of Leonard Gillman. In fact, I was present at one meeting where he advocated that and I watched the heated discussion that followed. I must say that his arguments convinced me that he is right. In fact, if you see the calculus text by Gillman & McDowell that is the convention in that book.

- Feb 17th 2009, 07:12 AM #3

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Other than the bases being different, they're pretty much the same thing, and of course you can use the

**change-of-base formula**to convert between the two.

Unless you are told which log to use, the choice should be up to you.

- Feb 18th 2009, 01:43 AM #4

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You may use which ever is best suited for your specific case.

For clarity you must define your base.

11*11 = 1001

That should seem obvious to most.

But some will insist that this is using binary.

Thus the base 2 is used.

My preference is ln

It is shorter.