if angleb is 120 then AC is 1202 = 240. 360-240 = 120 , 120/2 = 60 . If AB = 60 , angle adb is 30 and angle bdc is 30. DB is 2 radius because angleA is 90. So with Pisagor AB = 3 , BC = 3 , AD = 3root3 and DC is 3root3.
Answer is = 6+6root3 = 6(1 + root3)
