15 - What is a Logarithm (Log x) Function (Calculate Logs, Applications, Log Bases)

View more at . In this lesson, you will learn what a logarithm is and why they are important in all branches of math, science, and engineering. A logarithm is the inverse of the exponential function. This mean that a logarithm can reverse or “undo“ the exponential operation. This makes logs very useful for solving equations that have exponential terms. Physically, the logarithm is the reflection of the exponential curve over the 45 degree line y=x in the xy plane. We also learn the definition of the logarithm and how to convert an expression from log form into exponential form and vice versa.