Now watch how Ms. Davis worked on this problem in her classroom. This lesson was part of a three-week trigonometry unit. Earlier they had worked on graphing functions, adding functions, and the laws of sines and cosines.

As you watch, focus on how teacher questioning helped students improve their reasoning and clarified their use of mathematical terminology. Please watch the video excerpt at left of enveloping functions (duration 6:46).

  Think about the classroom you just watched