1. C is the midpoint of BD
1. given
2. BC ≅ CD
2. ♣
3. AC ≅ AC
3. reflexive property
4. ∠BCA and ∠DCA are right ∠s
4. given
5. ♦
5. all right ∠s are ≅
6. △ACB ≅ △ACD
6. SAS