Given: O is the midpoint of XY and of AB Prove: XA ≅ BY1. XO ≅ YO |1. O is the midpoint of XY 2. ∠XOA ≅ ∠YOB |2. vertical angles are congruent 3. AO ≅ BO |3. O is the midpoint of AB 4. ΔXOA ≅ ΔYOB |4. side-angle-side 5. XA ≅ BY |5. corresponding parts of congruent triangles Edwin