Trigonometry: An Informal Approach was thoroughly tested over a decade in the classroom and designed with the student in mind. The "Informal" description in the title refers to the style of explanation favored by the author, a conversational manner that attempts to engage the student and anticipates where more detailed explanations are needed. The reading level is appropriate for both high school and college students preparing for calculus, reflecting the author's 30 plus years of teaching the subject in both academic venues.