ABCD is a quadrilateral whose side AB is a diameter of a circle through A, B, C and D. If ∠ADC = 120°, then the measure of ∠BAC is?

30° 60° 45° 90°

30°

∠ACB = 90° ( in semicircle) ∠ABC = 180° - 120° = 60° (cyclic quad.) ∠BAC = (180° - (90° + 60°)) = 30°