Given a circle in which the diameter AB equals 9 cm. If two points C and D lie on the circle and ∠ABC = 20° and ∠BAD = 60°, find the length of the major arc CD.

Answer 1

20+60=80

80/360= 2/9

2/9 x 9pi=2pi cm

but "major" arc CD =9pi-2pi = 7pi

minor arc CD =2pi

or

360-80=280

280/360 =7/9 x 9pi =7pi