Sine, Cosine, and Tangent

In 3.1, the crank arm of a bike pedal spun around a center point, and the pedal's height followed a periodic pattern. To describe motion like that with a function, we first need a precise way to say how far something has turned. That is the job of this note: angles in the coordinate plane, and a new unit for measuring them called the radian. In 3.2B we will use these angles to define sine, cosine, and tangent.