The measure of an angle in radians is given by the formula:
\[ \theta = \frac{s}{r} \]
where \( \theta \) is the angle in radians, \( s \) is the arc length, and \( r \) is the radius of the circle.
In this case, the radius \( r \) is 6 feet and the arc length \( s \) is \( 2\pi \) feet.
Substituting these values into the formula:
\[ \theta = \frac{2\pi}{6} = \frac{\pi}{3} \]
Therefore, the angle measure in radians is:
\[ \frac{\pi}{3} \]
So the correct response is:
Start Fraction pi over 3 End Fraction.