As you drag the point (1, 0) along the vertical number line, a line segment is drawn along the vertical line from the point (1,0) to the point (1, [i]t[/i]). At the same time, an arc of length [i] t[/i] starting at the point (1, 0) is drawn along the unit circle. This shows how a real number t can be associated with an arc of length [i]t[/i] on the unit circle. This worksheet only allows t to go from -2*pi to 2*pi, so it does not show the rest of the vertical number line being "wrapped around" the unit circle.