This is a deep copy of the excellent open source textbook Trigonometry, by Michael Corral (Schoolcraft College). It has been a few years since I updated this file and is therefore getting stale. The official version can be found at http://mecmath.net/trig/. The official version is the ground truth. The author maintains a changelog/errata at http://mecmath.net/trig/changelog.txt as well as the tex source.