Sources used in this book:

"Basic Trigonometric Ratios." (accessed 06/17/11)., "Angle of Elevation." Last modified 06/27/2006. Accessed June 19, 2012. of elevation. Embracing Mathematics, Assessment & Technology in High Schools; A Michigan Mathematics & Science Partnership Grant Project

Holt, Rinehart & Winston, "Geology Application." (accessed 5/16/2011).

Holt, Rinehart & Winston, "Right Triangles and Trigonometry." (accessed 5/16/2011).

Holt, Rinehart & Winston, "Trigonometric Functions." (accessed 5/16/2011).

Math Interactives, "Exploring Trig Ratios." (accessed 5/16/2011)., "Angle of Elevation and Depression." Accessed June 19, 2012.

"Right Triangle and Applications." (accessed 06/20/11).

Weber, Keith. "Teaching Trigonometric Functions: Lessons Learned from Research." Mathematics Teacher, September 2008, 144 -150.