**Title:** Rolling Into Radians

**Description:**
Student groups collect height versus distance data for rolling objects of different sizes. Each group produces two sinusoidal graphs of the data, one in which both axes are measured in units, and the other in which both axes are re-scaled and free of units. Students note that the amplitude and period of the unit-free graph are the same for all groups, and then discuss how their measurement opens a different way of describing points on a unit circle.

**Standard(s): **

[MA2013] ALT (9-12) 37: Understand radian measure of an angle as the length of the arc on the unit circle subtended by the angle. [F-TF1]

[MA2013] ALT (9-12) 38: Explain how the unit circle in the coordinate plane enables the extension of trigonometric functions to all real numbers, interpreted as radian measures of angles traversed counterclockwise around the unit circle. [F-TF2]