1. The problem is to understand and apply CPCTC (Corresponding Parts of Congruent Triangles are Congruent). 2. CPCTC is used after proving two triangles are congruent by methods like SSS, SAS, ASA, AAS, or HL. 3. Once triangles are congruent, CPCTC states that all corresponding sides and angles are equal. 4. For example, if \triangle ABC \cong \triangle DEF, then \angle A = \angle D, \angle B = \angle E, \angle C = \angle F, and sides AB = DE, BC = EF, AC = DF. 5. To use CPCTC, first prove triangle congruence using one of the congruence postulates. 6. Then, state the corresponding parts that are congruent by CPCTC. 7. This helps in solving for unknown sides or angles in geometric problems. 8. CPCTC is a powerful tool to conclude equal parts without re-proving each part separately.