Each learning path is one chapter: a guided route through a topic, one small course at a time. Pick a class to see its chapters in order.
A Ferris wheel turns, a tide rises and falls, a guitar string shakes. Each motion repeats itself, and the trigonometric functions describe all of them. In this chapter you measure angles in radians, extend sine, cosine and tangent to angles of any size with the unit circle, draw their graphs, and prove the formulas for the sum and the difference of two angles. Python draws the graphs and checks each identity at thousands of angles.