Question

In the figure given alongside, AB and CD are straight lines through the centre O of a circle. If ∠AOC = 80° and ∠CDE = 40°, find the number of degrees in ∠ABC.

Answer 1

In ΔBOC,

∠AOC = ∠OCB + ∠OBC

(Exterior angle of a Δ is equal to the sum of pair of interior opposite angles)

`=>` ∠OBC = 80° – 50° = 30°  ...[∠AOC = 80°, given]

Hence, ∠ABC = 30°