By definition, the arc length is given by:
s = R * teta
Where,
Radio
Teta: arc angle measured in radians.
We have then that the length of the arc in this case is:
s = (7.9) * (180-66.4)) * (pi / 180)
s = 15.7 cm
Answer:
The length of the AD arc is:
s = 15.7 cm