This looks like a fill-in the blanks question for a two column proof :]
3. CPCTC
The reasoning for this is that because triangle ABC and EDC are congruent, their corresponding parts are also congruent, (CPCTC; Corresponding Parts of Congruent Triangle are Congruent) or AC = EC
4. ACE
Because AC = EC, triangle ACE is isosceles
5. Base Angles Theorem
The base angles of a isosceles triangle are congruent
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