Trigonometry: An Annotated Bibliography
Aaboe, Asger, Episodes from the early history of mathematics, Washington: Mathematical Association of America, c1964.
A Sourcebook of Applications of School Mathematics, NCTM 1980.
There is a nice chapter on applications involving trigonometry and logarithms.
Andreescu, Titu, and Feng, Zuming, 103 Trigonometry Problems: From the Training of the USA IMO Team, Boston: Birkhäuser, 2005.
This work begins with a succinct (62 pages) summary of trigonometry. Then come the problems. The first one is "Let x be a real number such that sec x - tan x = 2. Evaluate sec x + tan x." Then the problems get hard. Solutions are provided. If you encounter an exceptionally good student, give them a copy of this book and encourage them to work hard on the problems.
Berlinghoff, William P. and Gouvêa, Fernando Q., Math through the Ages: A Gentle History for Teachers and Others , Oxton House, 2002.
Courant, Richard (1888-1972) and Robbins, Herbert, What is mathematics?, London, New York, Oxford university press [c1941].
Euler, Leonhard, Introduction to Analysis of the Infinite, Book I, Springer-Verlag, 1988.
English translation of Euler's famous Introductio in analysin infinitorum of 1748. Here is a "Reader's Guide."
Fellmann, Emikl A., Leonhard Euler, Birkhauser 2007.
The best biography of Euler in English (but a poor translation from the German).
Gelfand, I. M. (Izrail Moiseevich) and Saul, Mark, Trigonometry, Boston: Birkhäuser, 2001.
An excellent basic book.
Grinstein, Louise S. and Michaels, Brenda, Calculus. Readings from the Mathematics Teacher, NCTM 1977.
A nice source of presentation topics.
Goldstine, Herman H., A History of Numerical Analysis from the 16th through the 19th Century, Springer-Verlag, 1977.
Historical topics for the mathematics classroom. [Editorial panel: John K. Baumgart, Duane E. Deal, Bruce R. Vogeli, and Arthur E. Hallerberg]. Thirty-first yearbook of the National Council of Teachers of Mathematics, 1969. There is also a later edition.
There is a brief history of trigonometry by Edward S. Kennedy.
Moar, Eli, Trigonometric Delights, Princeton University Press, 1998.
Steinhaus, Hugo, Mathematical Snapshots,
Toeplitz, Otto, The Calculus. A Genetic Approach, University of Chicago Press, 1963.
Usiskin, Zalman; Peressini, Anthony; Marchisotto, Elena Anne; and Stanley, Dick, Mathematics for High School Teachers: An Advanced Perspective, Prentice-Hall, 2003.
Chapter 9 deals with trigonometry.