arc length formula is s = r*theta, where s is the arc length and theta is the angle in radians (not degrees).
Here, we must convert 38 degrees to radians:
38 deg pi rad
----------- * ------------- = 0.211 pi radians = 0.663 rad
1 180 deg
Then the arc length is (20 ft)(0.663 rad) = 13.26 ft
