Answer: before you can use the reason CPCTC it must be stated that the triangles are congruente.
Step-by-step explanation:
1) CPCTC stands for Corresponding Parts of Congruent Triangles are Congruent.
2) Therefore, to use that reason you first need to prove that the the triangles are congruent.
3) Once, it has been stated that the triangles are congruent, then you can use the reason to state the the corresponding segments are congruent which will let you to state the length of any side of one triangle known the corresponding side of the other triangle, because they are congruent (have the same length).