There are two kinds, log and LN (natural log), but I don't know when to use them.

How do I know when to use log or LN for a problem? How can I determine that?

Please help. Thank you!

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Originally Posted by survivorboi

There are two kinds, log and LN (natural log)

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Actually, those are just two of the infinite types of logarithms. You can have logarithms to any base. The two you've specified are base 10 and base e. Remember that a logarithm is an exponent. For LOG it is 10^x = y where x is the exponent. This is the same as x = LOG(y).

If an equation already contains LN or LOG, you have to use the same base to solve the equation. Often you'll use the antilog and you have to use it to the correct base. For LN, the antilog is e^x and that is often expressed as EXP(X).

For many equations, it simply doesn't matter. For example take this equation and solve for X:

X^5 = 35
LN(X^5) = LN(35)
5 LN(X) = LN(35)
5 = LN(35)/LN(X)

and
LOG(X^5) = LOG(35)
5 LOG(X) = LOG(35)
5 = LOG(35)/LOG(X)

Both answers are correct. Both answers give the same number.