These three posts discuss the development of this diagram:
Whenever I show this diagram to students, they seem actually excited to discover the meaning and reasons behind so much trigonometry that they had previously just memorized. It makes me believe that it would be helpful if this diagram was displayed in every room where trigonometry is introduced. And now it can be! I tidied up the graphics and made it into a poster.
Here it is, available to download, in two convenient sizes:
For your notebook (8.5″ x 11″) Trig Diagram Notebook-sized
For your wall (22″ x 28″ ) Trig Diagram Poster-Sized
Also, I recently gave a workshop about this. You can see the slides here.
COMING SOON: T-SHIRTS!! (Maybe)