Final answer:
To prove that triangles ABC and CBA are congruent, we can use the transitive property of parallel lines to show that they share a common side. Similarly, we can prove that they have a common angle. Therefore, by the Side-Angle-Side (SAS) congruence postulate, we can conclude that ABC and CBA are congruent triangles, resulting in AB ≅ BC.
Step-by-step explanation:
To prove that τABC and τCBA share a common side, we can use the transitive property of parallel lines. Since τCBE and τABC share a common side, and τCBE and τ2019CBA share a common side, then τABC and τCBA also share a common side.
Similarly, we can prove that τABC and τCBA have a common angle. Since τCBE and τABC have a common angle at B, and τCBE and τ2019CBA have a common angle at B, then τABC and τCBA also have a common angle at B.
Therefore, by the Side-Angle-Side (SAS) congruence postulate, we can conclude that τABC and τCBA are congruent triangles, and thus the sides AB and BC are congruent, as stated in the given statement.