In the following figure, MN is a tangent to a circle with centre O at point A. If BC is a diameter and ∠ ABC = 42°, then find the measure of ∠ MAB.

84° 48° 42° 45°

48°

According to the concept ∠BAC = 90° So, ∠BCA = 180° - 42° - 90° ⇒ 48° Now, according to the concept ∠MAB = ∠BCA So, ∠MAB = 48° Therefore, ∠MAB is 48°