Segments AB and CD intersect at point O. CO = OD, ⦟ BCD = ⦟ CDA. Prove that AD = CB.

Given:

segments AB and CD,

point O – the point of intersection of segments AB and CD,

CO = OD,

angle ВСD = angle СDА.

Prove that AD = CB.

Evidence:

Consider triangle AOD and triangle COB. Angle AOD = angle of COB, as these angles are vertical angles. Angle ВСD = angle СDА and СО = ОD according to the problem statement. Therefore, triangle AOD = triangle COD along the side and two adjacent corners. Then AD = BC. Q.E.D.



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