Question

The sides AO and BO have been extended such that AO = OC and BO = OD. Prove that CD II AB.
​

Answer 1

Given,

OB = OD

AO = OC

and as we can see,

angle AOB = angle DOC (vertically opposite angles)

So,

∆AOB is congruent to ∆DOC by SAS property.

So,

by cpct:-

angle BOA = angle OCD

These are alternate interior angles and hence,

CD II AB

Cheers!