This guide covers the story of trigonometry. It is a swift overview, but it is complete in the context of the content discussed in beginning and advanced high-school courses. The purpose of these notes is to supplement and put into perspective the material of any course on the subject you may have taken or are currently taking. (These notes will be tough going for those encountering trigonometry for the very first time!)

In reading and working through the material presented here you will

1. • see the story in of trigonometry in a new light,

2. • see the reasons why we, mankind, developed the subject in the way we did,

3. • begin to move away from memorization and half-understanding to deep understanding, and thereby

4. • be equipped for agile, clever thinking in the subject.

These notes will guide you through to sound mathematical doing in trigonometry and, of course, to sound problem-solving skills as well.