Trigonometry: History
Trigonometric functions
History of Mathematics
Geodetic surveying 1940-1990
Spherical Trigonometry
Earliest Clocks
River Crossing
Fundamental Formulae

TRIGONOMETRY APPLICATIONS

If you are having trouble deciding upon a topic for research you might consider looking at this
site to get a general  background about the uses of trigonometry:
 

Here are a few more sites that discuss the use of trigonometry:
Archaeogeodesy    http://www.jqjacobs.net/astro/aegeo_4.html
Calculating Distance   http://www.meridianworlddata.com/Distance-Calculation.asp
Celestial Navigation  http://www.ece.gatech.edu/research/labs/globe/globe3/erad7/ERAD7.HTM
Earthquakesl

EAAE-AOL : Simple Trigonometry - distance towards Saturn
Columbus and Celestial Navigation
RE: Measurement of the distance between the Earth and the Sun
Applications of trigonometry
Angle Measurement         http://www.sli.unimelb.edu.au/Horizons/Documents/angle.html
Global Position System     http://www.sli.unimelb.edu.au/Horizons/Documents/gps.html
Photogrammetry   http://www.sli.unimelb.edu.au/Horizons/Documents/photo.html
Positioning on the Plane   http://www.sli.unimelb.edu.au/Horizons/Documents/plane.html
Remote Sensing    http://www.sli.unimelb.edu.au/Horizons/Documents/rs.html