*Logarithms* are the *inverse functions *of exponential functions. They help us solve for an exponent.

If I have , this is read “log base b of c.”

The base is the same base as the base of an exponent. The answer you get when you evaluate this is the same as the exponent. The relationship between between a and an exponent is the same as the relationship between division and multiplication.

and

**Evaluating (easy) Logarithms**

Evaluating logarithms is just about finding the number that would make the exponent work.

(3 to what power is 9?)

### Common Logs & Natural Logs

Most logarithms, like the ones on your calculator, are either , written simply as , or , written as . is called common log, and is called a natural log. Most calculators have buttons for common logs and natural logs, but not any other type of log.