1. ∠CDE ≅ ∠CED Given. 2. ΔCDE is isosceles It has two congruent angles, from 1. 3. CD ≅ CE Congruent sides of isosceles triangle CDE, from 2. 4. ∠ADC ≅ ∠BEC Supplements of congruent angles are congruent, from 1. 5. AD ≅ BE Given. 6. ΔADC ≅ ΔBEC SAS, from 3,4, and 5 7. AC ≅ BC Corresponding parts of congruent triangles, from 6. 8. ΔACB is isosceles ΔACB has two congruent sides, from 7. Edwin