Trigonometry formulas (Image credit: Olga Leonichenko)

What comes to mind when you hear the words sine, cosine, and tangent? You might think that it has something to do with math. But do you know where these terms specifically fall under the mathematical umbrella? If you guessed trigonometry, or “trig” as some people like to call it, you would be correct.

Trigonometry is a form of mathematics that primarily deals with trigonometric functions. These functions are used to relate the angles of a triangle to the length of the triangle’s three sides. The sine function of an angle is the ratio of the length of the opposite side to the length of the triangle’s hypotenuse. The cosine of an angle is the ratio of the length of the adjacent side to the length of the hypotenuse. Finally, the tangent function of an angle is the ratio of the length of the opposite side to the length of the adjacent side of the triangle. “SOHCAHTOA” is an acronym that many trig teachers encourage their students to memorize in order to remember what sine, cosine, and tangent represent.

Although trigonometry is a fairly specific subject that is included as an individual chapter in many math textbooks, several textbooks exist that are mostly dedicated to this topic. Because of this, you will likely learn trig better if you use these books because each chapter is designed to provide small steps in the learning process compared to one chapter in a larger book that would provide a more general overview. has ranked the top 10 trigonometry textbooks.

1) Algebra and Trigonometry by Michael Sullivan (2007 – Prentice Hall)

2) Algebra and Trigonometry: Structure and Method by Richard G. Brown (1999 – McDougal Littell)

3) Trigonometry by Charles P. McKeague and Mark D. Turner (2007 – Brooks Cole)

4) Algebra and Trigonometry Plus MyMathLab Student Access Kit (4th Edition) by Robert F. Blitzer (2009 – Prentice Hall)

5) Trigonometry, Ninth Edition by Margaret Lial, John Hornsby, and David I. Schneider (2008 – Addison Wesley)

6) Algebra and Trigonometry, Enhanced Edition by James Stewart, Lothar Redlin, and Saleem Watson (2009 – Brooks Cole)

7) Student’s Solutions Manual for Trigonometry by Margaret L. Lial, John S. Hornsby, and David I. Schneider

8) College Algebra (College algebra and Trigonometry Series) by Richard M. Aufmann (1989 – Houghton Mifflin School)

9) Precalculus With Unit-Circle Trigonometry by David Cohen (2006 – West Publishing Company)

10) Physics Algebra/Trig Student’s Solutions Manual by Eugene Hecht (2002 – Brooks Cole)

These books and others can be found by using You can quickly and easily compare prices on almost every textbook on the market by searching for the title of it or the ISBN number. This site also contains a huge database of bookstores at various universities around the nation. To find the best prices on new, used, rental, or digital textbooks, you’ve come to the right place!