Heeding Dan's encouragement to step things up in his NCTM talk, I revisited an introduction to functions activity that I put together three years ago.
I put together this three-act activity two years ago, and decided to include it in the playlist for this year's Math 9 course. The students
Graphing trigonometric functions is a crucial skill, but there is a lot of reasoning involved in the process. I learned the method that follows from