Move the slider to change the radius length.
Move point P until the measure of the radius is the same as the length of the arc.

1. What are the measures of the radius and the purple arc?
2. How many times larger is the arc of a 360 degree angle than the radius?
3. Move point P until the measure of the arc equals the radius. This measure correspondes to 1 radian.
4. Move point B and observe: What measurements change? What measurements stay the same?
5. What angle is bigger, one that measures 1 radian or one that measures 60 degrees?
6. Imagine an angle that measures 2 radians, how many degrees would that be? How about 5 radians? 1/2 radian? Check your answers in the construction.
7. In your own words, what is a radian?
8. Imagine a 180 degrees angle, what is the measure in radians? Is this reasonable? How many radians is a 90 degree angle? A 360 degree? why?