Sine function graph with unit circle

Jon Dreyer
Relationship of the unit circle and radian measure and the sine function. Drag the big blue point labeled θ and see how that affects the angle in the unit circle and (in radian measure) the arc length also labeled θ. So according to the unit circle definition of the sine function, that is the y coordinate of the point labeled (cosθ, sinθ). Superimposed on the unit circle picture is a function graph of the sine function, in which the x-axis represents θ. Convince yourself that the point labeled (θ, sinθ) is labeled correctly. Experiment with different values for θ, both positive and negative.