Explain why ΔABC cannot be shown to be congruent to ΔCDA.
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There isn't enough info to prove the triangles to be congruent or not. So we can't say for sure either way.
We have angle CAD = angle ACB given by the arc markings, and we know that AC = AC due to the reflexive theorem. However we are missing one third piece of information.
That third piece of info could be....
Since we don't know any of those three facts, we simply don't have enough information.
side note: If AB = CD, then this leads to SSA which is not a valid congruence theorem. If we had two congruent sides, the angle must be between the two sides, which is what AD = BC allows.