1. Triangle Proportionality Theorem:
If a line parallel to one sides of a triangle intersects the other two sides, then it divides the two sides proportionally.
2. Converse of Triangle Proportionality Theorem:
If , then SP II QL
3. If three parallel lines intersect two transversals, then they divide the transversals proportionally
4. If a ray bisects an angle of a triangle, then it divides the opp. side into segments whose lengths are proportional to the lengths of the other two sides.
If BD bisects ∠ ABC in Δ ABC, then