Khan Academy: Pre-Calculus
Khan Academy

The Precalculus course, often taught in the 12th grade, covers Polynomials; Complex Numbers; Composite Functions; Trigonometric Functions; Vectors; Series, Conic Sections, Probability and Combinatorics.

Khan Academy: Algebra 2
Khan Academy

Course summary:  Polynomial arithmetic · Complex numbers · Polynomial factorization · Polynomial division · Polynomial graphs · Rational exponents and more.