Do you teach trig? Do you wish your students had a solid understanding of how to relate trig ratios beyond 90 degrees to the unit circle? Are you tired of kids asking which button to press?
Well … I can’t say for sure if this solves your problem, because I haven’t used it in my class yet. But someone else has! And they said it works great!
The original I was shown is simply a full-circle protractor photocopied onto a co-ordinate grid. I decided to make a fancy-looking version in Illustrator. And since I’m all proud of it, I’m sharing it with all y’all.
The idea is, if you want to look up sin or cos for a given angle, just find the angle and then read the y or x co-ord of the matching point on the unit circle. Kids should be able to visually estimate something close to two decimal values worth.
Enjoy!
Edit: You may also want to check out the matching 30-60-90 and 45-45-90 triangle cutouts that match.
Same idea, more accuracy: http://www.mathedpage.org/circle/