Since BC is congruent to EC, and AC is congruent to DC. Then that must mean they have the same angles which declares that both triangles are the same shape so that means that BA is congruent to ED. Also put that by the law of CPCTC (Congruent parts of congruent triangles are congruent), these angles are all equal to one another. If one angle equals the other they all equal the other.
