Chapter 1 begins with the geometric (right triangle) definition of sine, cosine and tangent. It then develops the unit circle and the trigonometric definitions of sine, cosine and tangent. It does not discuss the connection between the geometric and unit circle definitions, as that is more appropriate for a formal geometry course. The chapter ends with other properties of trig functions, including the reciprocal functions.
Trigonometry by Mike Weimerskirch and the University of Minnesota Board of Regents is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License, except where otherwise noted.