High school and college students, who have completed high-school courses in algebra and geometry, should be prepared for undertaking a course on trigonometry and using this free online trigonometry textbook. It was written by Michael Corral from Schoolcraft College.

Corral believes that many trigonometry books place too much emphasis on analysis. His work starts with the “old-fashioned” right triangle approach to trigonometric functions which he believes is easier for students to understand. Rather than trying to force associations between the “real world” applications of trigonometry, he focuses on how the math will be utilized in later courses. After all, how many people use protractors to determine the height of a tree or determine the speed of a Ferris wheel.

His trigonometry textbook was derived from his lecture notes with the addition of hundreds of practice problems. He includes answers to the odd-numbered problems as well as some of the even ones. What I think is a great idea is that for some of the problems, he includes hints. For example, one exercise asks students to prove the Cofunction Theorem. He provides the hint, within the text and not near the tempting answer key, “draw a right triangle and label the angles and sides.”

## Chapter Titles from Trigonometry, a Free Online Textbook

- Right Triangle Trigonometry
- General Triangles
- Identities
- Radian Measure
- Graphing and Inverse Functions
- Additional Topics
- Appendix A: Answers and Hints to Selected Exercises
- Appendix B: Graphing with Gnuplot

View this Free Online Material at the source:

Trigonometry