Triangle ABD is inscribed in circle and has hypotenuse as circle's diameter so angle ABD must be 90°
Since it is parallelogram, ∠ABD = ∠BDC = 90° and it is given that ∠ADB = 30°
So we have ∠CDO = ∠CDB + ∠ADB = 30° + 90° = 120°
Final answers: ∠CDO = 120° and ∠ABD = 90°
