Triangles in combination

So far, students have been creating 30, 45, 60 and 90 degree angles with the use of a single triangle.  Would you believe that you can also create 15, 75 and 105 degree angles as well?  IMPOSSIBLE you say?  Oh, it's possible...find out more next week when we start Aim #10: How do we use triangles in combination? 
Here's the download link for the .pdf file with all the details.