PURPOSE: To remind students of the definitions of sine and cosine.

DESCRIPTION: Slowly rotate the unit circle of radius R. Students can easily observe the opposite side and the adjacent side as the angle is changed. This provides a dynamic sense of the values of the sine and cosine in the first two quadrants.

SUGGESTIONS: K7-46 is a similar demonstration that is newer and easier to use.

REFERENCES: (PIRA 1A50.30)

EQUIPMENT: Disc-mounting rod assembly, wood stand with table clamp, metal stand with right-angle clamp, two stick pointers, nail; assembled as photographed on request.

SETUP TIME: 15 min.