The formula for arc length as a function of the radius and central angle is
s = r*theta, where theta must be in radians.
This 80 degree central angle converts to radians as follows:
80
------ * 2*pi, or (160 pi)/360, or 1.396 radians
360
Thus, the arc length is s = (7 inches)(1.396 radians) = 9.774 inches.
