#### Welcome to the sample chapter of the interactive logic textbook!

Logic is a tool that helps us solve problems. Scientists use logic to figure out what theory their data supports. Mathematicians use logic to prove things like the Pythagorean theorem. Children use logic to solve Sudoku puzzles and win chess games.

You can't learn logic without using it. That's one reason why this textbook is interactive.

There are two types of problems in the book. **Practice problems** are mixed into each section. They are there to help you learn: they aren't worth points, and if you get them wrong, you get to try again.

**Exercise problems** occur at the end of the chapter. They help you extend your understanding and combine ideas learned in different sections. The exercise problems count toward your homework grade, but you can retry them as well, up until the due time set by your instructor.

Look for **key concepts** in the call-out boxes.

The point of letting you try again is so the harder you work, the more you will learn and the better you will do.

Let's try it out.