In the circle below, AB is parallel to CD, AD is a diameter of the circle, and AD = 36.What is the length of AB?
Let O be the center of the circle....draw radii OA and OB = 18
Triangle OAB will be isoceles with angle AOB = 180 - 2*42 = 180 = 84 = 96°
By the Law of Sines
AB /sin 96° = OB /sin 42°
AB / sin 96° = 18 / sin 42°
AB = 18 * sin (96°) / sin 42° ≈ 26.75
