Question

Chord AB subtents angle AOB= 60degree at the centre of the circle. If OA =5cm find the length of AB.

Answer 1

Here, OA = OB = r [radii of same circle]



⇒ ∠A = ∠B ----- (i)

In ΔOAB,

∠O + ∠A + ∠B = 180°

⇒ 60° + ∠A +∠A  = 180° [using eq. (i)]

⇒ ∠A = 60° 

Thus ∠O = ∠A = ∠B = 60°