Precalculus
Functions and trigonometry, in the depth a first calculus course expects.
1,129 interactive problems, free to use.
The course between Algebra 2 and calculus. It covers the function work and trigonometry that a first calculus course expects students to have already, with extra time on transformations, the unit circle, and rational functions.
Graphing problems are interactive: the student works directly on the coordinate plane.