Question

Which theorem or postulate can be used to justify triangle ABC ≈ triangle CDA?

Answer 1

It is given that:

$AB\parallel DC\text{ and }AD\parallel BC$

So the angles congruent by alternate angles theorem are:

$\begin{gathered} \angle\text{DAC}\approx\angle\text{ACB} \\ \angle DCA\cong\angle CAB \end{gathered}$

With AC as the common side the triangles ABC is congruent with triangle CDA by ASA postulate.

ASA is correct.