∠ABC = ∠CDA (given)
∠BCA = ∠DAC (given)
CA = AC (common side)
ASA congruence criterion = when two angles of two triangles are equal and their included side is also equal, we can consider those triangles to be congruent to each other.
Since two angles in triangle △ABC and△CDA are equal and since their included side is also equal we can conclude that they are congruent.
Therefore, △ABC ≅ △CDA under the ASA congruence criterion.
