Statement Reason 1. Define the vertices of ΔABC to have unique points A(x1, y1), B(x2, y2), and C(x3, y3). given 2. Let D be the midpoint of and E be the midpoint of . defining midpoints 3. 4. Slope of slope of definition of slope 5. Slope of = slope of Transitive Property of Equality 6. Is parallel to definition of parallel lines 7. Let F be the midpoint of . defining a midpoint 8. definition of midpoint 9. Slope of slope of definition of slope 10. Slope of = slope of Transitive Property of Equality 11. Is parallel to . definition of parallel lines 12. Similarly, is parallel to . steps similar to steps 1-11 18 What is the reason for statement 3 in this proof?