Texas Instruments
Texas Instruments: Angle Theorem
Students use the Cabri Geometry II Plus software to investigate the relationship between angle and ratio in a right triangle.
Other
Advogato: Trigonometry by Geometric Construction
This site from Advogato is all about angles. It contains information starting with what an angle is and what it looks like, all the way up to bisecting angles and theorems about angles. This is very good information for students just...