Free college algebra textbook written by two Ohio educators. A truly living text supported by a forum where students are encouraged to ask questions.
Free Precalculus Textbooks
Just as the name implies, precalculus is designed to prepare students moving on from basic mathematics to more complex math concepts. Precalculus textbooks typically build upon earlier courses in algebra and geometry and introduce trigonometry and calculus. Students will work with sets, functions, matrices, vectors and a number of other topics. Prerequisites are two years of algebra and a year of geometry.
High schools and universities offer precalculus courses though at the college level they are sometimes called college algebra or trigonometry. The free online precalculus textbooks that I have found were written for students at all levels. If you are having trouble, you might want to see if one or more of these textbooks are written in such a way that you can understand the material better.
List of Free Precalculus Textbooks
College Algebra
Dave’s Short Course on Trigonometry
The author might call this a short course on trigonometry but I think it would make a great refresher course or supplementary text for students.
Free Precalculus Textbook
Free precalculus textbook from a pair of true educators. The authors have an open forum and appear happy to answer questions from students and educators.
High School Free Precalculus Textbook
A high school in Texas has shared a free precalculus textbook for the use of their students and anyone else with an active Google account.
Precalculus
Precalculus, a textbook written by two calculus professors hoping to better prepare their students for the rigors of calculus courses.
Precalculus: An Investigation of Functions
Precalculus textbook which embraces the open textbook initiatives and works with real world examples like age, height, gas prices and even taxi fares.
Trigonometry
Free online trigonometry textbook by Michael Corral from Schoolcraft College. Geometrical rather than analysis approach, focus on preparation for later math courses.
Trigonometry
Free online trigonometry text that starts with a circular function approach to trigonometry and moves on to the study of triangle trigonometry, vectors, trigonomic identities, and complex numbers.