Question

What is the answer for (b)?​

Answer 1

(b) ∠ADC = 60°

Explanation:

ΔBOC is isosceles and M is the midpoint of BC

then

∠MOC = ∠BOM = 30°

then

∠BOC = 60°

……………………

OC // AB

then

∠ABO = ∠BOC = 60° (alternate-interior angles)

……………………………………………

In ΔOAB ,we have :

OA = OB and ∠ABO = 60°

Then ,

ΔOAB is an equilateral triangle.

then

∠AOB = 60°

……………………………

We get :

∠AOC = ∠AOB + ∠BOC = 60° + 60° = 120°

……………………………………………………

∠ADC = ∠AOC/2 = 120/2 = 60°