In this video the teacher uses the Motion of a Fly GSP to discuss what happens when there is a negative change in amount.
Worksheet 4, Clip 4, Discussion of Rate of Change of Cosine Function II, 2:29
As he did in the previous clips, the teacher again uses the applet with a constant change in the arclength (input) and has the students firgure out what the corresponding change in the output will be. In this case the teacher moves the applet so that a negative change occurs.
To aid the students he has them attend to the magnitude of the change, not just the sign. This helps the students identify how it is changing. As they talk about how it is changing, the teacher also makes the move to draw the graph on the board. This will aid the students in making the connection between the way cosine is changing and its graphical representation.Having this meaning behind the shape of the graph will help students recall what it looks like.
