Explanation:
Statement: ΔABC, CA ≅ CB
Reason: Given
Statement: ΔABC is an isosceles triangle
Reason: Definition of an isosceles triangle
Statement: ∠A ≅ ∠B
Reason: Properties of isosceles triangles
Statement: AR ≅ BS, DR ⊥ AC, DS ⊥ BC
Reason: Given
Statement: ΔARD ≅ ΔBSD
Reason: ASA congruence
Statement: DR ≅ DS
Reason: Corresponding parts of congruent triangles are congruent