The length of the semi-circle below is [math]\pi[/math] units. Move the slider to rotate the ray so that it cuts an arc with length a) [math]\frac{\pi}{2}[/math] units, b) [math]\frac{\pi}{3}[/math] units c) [math]\frac{\pi}{4}[/math] units, and d) [math]\frac{\pi}{6}[/math] units. Use the boxes beside the figure to check your work!