# Introduction to logarithms

5 videos

3 skills

Learn how we define logarithms and use this definition in order to evaluate various logarithms. For example, evaluate log_2(8) as 3 by realizing that 2^3=8.

### Introduction to logarithms

VIDEO
7:02 minutes

Sal explains what logarithms are and gives a few examples of finding logarithms.

### How to rewrite exponential equations in logarithmic form and vice versa (example)

VIDEO
1:42 minutes

Sal rewrites 100=10^2 as a logarithmic equation and log_5(1/125)=-3 as an exponential equation.

### How to plot points of a logarithmic function that correspond to the inverse exponential function (example)

VIDEO
4:10 minutes

Given a few points on the graph of an exponential function, Sal plots the corresponding points on the graph of the corresponding logarithmic function.

### How to find missing values in tables of inverse exponential and logarithmic functions (example)

VIDEO
5:59 minutes

Given incomplete tables of values of b^x and its corresponding inverse function, log_b(y), Sal uses the inverse relationship of the functions to fill in the missing values.

### The inverse relationship of exponents and logarithms

PRACTICE PROBLEMS

Solve various problems that focus on the relationship between a^x=b and log_a(b)=x.

### Evaluate logarithms (basic)

PRACTICE PROBLEMS

Evaluate basic logarithmic expressions by using the fact that a^x=b is equivalent to log_a(b)=x.

### How to evaluate advanced logarithmic expressions (example)

VIDEO
4:20 minutes

Sal evaluates log_2(8), log_8(2), log_2(1/8), and log_8(1/2).

### Evaluate logarithms (advanced)

PRACTICE PROBLEMS

Evaluate advanced logarithmic expressions by using the fact that a^x=b is equivalent to log_a(b)=x.