Multiple choice

In a circle with centre O, AOC is a diameter of the circle, BD is a chord and OB and CD are joined. If ∠AOB = 130o, then ∠BDC = ?

  1. 30o

  2. 50o

  3. 25o

  4. 60o

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Angle BDC is half of angle BOC. Since AOC is a diameter, angle AOC=180°, so angle BOC=180-130=50°. Angle BDC=50/2=25° (angles in the same segment are equal). This tests circle geometry: angle at center is twice angle at circumference.