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OA = OD, angle 1 = angle 2
Angle COA = angle BOD

two angles and one side are equal between the two triangles AOC and DOB.
Triangles AOC and DOB are similar.

So, CO = BO
So OCB is an isosceles triangle.

2 4 2
Sir, can you explain why Angle COA is equal to Angle BOD
when two straight lines intersect at a point, the angles included by the two lines at that point, on the same side of a line sum to 180 deg. The opposite angles are equal. this is the reason for angle COA being equal to angle BOD.