# Alg2.6 Trigonometric Functions

In this unit, students are introduced to trigonometric functions. While they have studied a variety of function types with different key features previously, this is the first time students are asked to consider periodic functions, that is, functions whose output values repeat at regular intervals. Students first consider circular motion and learn to use right triangle trigonometry to identify the coordinates of a point on a circle. The unit circle is introduced, and students study the symmetry of its coordinates and reason about radian angles knowing a full circle has an angle of \(2\pi\). From the unit circle, the domain of cosine, sine, and tangent are expanded and students begin to think about them as functions. Students graph these functions using their knowledge of the unit circle and expand the domain of the functions a second time to angles beyond \(2\pi\) and less than 0. The second half of this unit builds directly on the work of the previous unit by having students apply their knowledge of transformations to trigonometric functions and use these functions to model periodic situations.