Question

Plz help me getting no 26.....plz

Answer 1

Answer:

Hope this is helpful.

There appears to be an issue with this problem as the conclusion is not true in general.  It is only true when ∠BAC = 60°.

If ABO'C were a parallelogram, then

∠CBO' = ∠ACB   [ since BO' parallel to AC ]

= ∠ABC   [ by symmetry about the line AO ]

Also, ∠CBO' = ∠DBO'   [ by symmetry about BO' ].

So the three angles ∠ABC, ∠CBO', ∠DBO' at B would all be equal and yet form a straight line, so the would all equal to 60°.

In particular, this means the triangle ABC would need to be equilateral for ABO'C to be a parallelogram.

Without the additional information that ∠BAC = 60°, it is possible that ABC is not an equilateral triangle, and therefore ABO'C in not a parallelogram after all!