Question

plz koi solve kar do
ASAP
of class 9

Answer 1

Given : O is the centre of the circle and AB is a diameter. AC is chord of circle.

To prove : ∠A = 1/2 ∠COB

Solution :

Since AO = CO ( radius of circle ), the ∆ AOC is an isosceles triangle, angle opposite to equal side will also be equal.

So,

• ∠CAO = ∠OCA

Therefore, applying exterior angle property of triangle according to which, sum of two interior angles is always equal to exterior angle.

So,

⇒ ∠CAO + ∠OCA = ∠COB

⇒ ∠CAO + ∠CAO = ∠COB

⇒ 2 ∠CAO = ∠COB

⇒ ∠CAO = 1/2 ∠COB

⇒ ∠A = 1/2 ∠COB

Hence proved.