Question:
In figure, if ∠AOB = 125°, then ∠COD is equal to
(a) 62.5°
(b) 45°
(c) 35°
(d) 55°
Solution:
(d) We know that, the opposite sides of a quadrilateral circumscribing a circle subtend supplementary angles at the centre of the circle.
i.e., $\quad \angle A O B+\angle C O D=180^{\circ}$
$\Rightarrow \quad \angle C O D=180^{\circ}-\angle A O B$
$=180^{\circ}-125^{\circ}=55^{\circ}$