∠AOC= 120? ,∠COB=60? ;
∠CAB=30? (The circumferential angle on the same arc is equal to half the central angle),
∠CBA=60? ,∠ACB =90? The circumferential angle on the diameter is a right angle.
And ∠ CDB = 3 ∠ cab = 90? . ∠BCD =30? .
BC = 8 (right angle △ right angle side is equal to half of hypotenuse) = OB (△ OCD is equal to side, and the inner angle is 60? ),
AB= 16 .
∵∠ACD∠BCD = 60? ∶30? = 2:1,so AD = 16×? .
∴△CAD area = AD CD=? × 16×? ×6=32。