1. Assume AB and CD bisect each other | 1. Assumption for indirect proof 2. AE is congruent to BE | 2. E bisects AB 3. CE is congruent to DE | 3. E bisects CD 4. Angle AEC is congruent to angle BED | 4. Opposite (vertical) angles 5. Triangle AEC is congruent to triangle BED | 5. SAS 6. DB is congruent to AC | 6. CPCT 7. DB is not congruent to AC | 7. Given 8. AB and CD do not bisect each other | 8. 6 and 7 contradict assumption 1 Edwin