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The Flash "movie" allows students to see the flow of function values as the dot circles the centre point or origin. Students can be encouraged to see the "spot" values provided by a calculator as snap-shots of this flow.
Check that students grasp that an angle of zero is when the dot is at (1,0), that the red line corresponds to the Sine value and the blue line to the Cosine value.There may be a need to guide students into noticing that there is a the change of sign, and noticing when it occurs.