Several open-source mathematics textbooks are available online, including "College Trigonometry 3rd Corrected Edition" by Stitz Zeager, "Precalculus 3rd, Corrected Edition" by Lakeland Community College and Lorain County Community College, and "A First Course in Linear Algebra" by Robert A. Beezer. The copyright situation for these materials has been verified. Users should be cautious as the navigation buttons for page turning may be ineffective.