Khan Academy: Precalculus
By Khan Academy
Khan Academy is one of the leaders in free online education, with the majority of courses being taught by Salman Khan, the site’s founder. It offers a personalized learning resource for all ages delivering interactive courses via videos and practice exercises.
The tutorials in the Precalculus program give you the background for the mathematical concepts, problems, issues and techniques that appear in calculus, including trigonometry, functions, complex numbers, vectors, matrices, and others.
Math 1A/1B: Pre-Calculus (English)
By The University of California Irvine
This Pre-Calculus course is designed to prepare students for a calculus course. This course is taught so that students will acquire a solid foundation in algebra and trigonometry. The course concentrates on the various functions that are important to the study of the calculus.