PROVING A THEOREM Use the diagram to prove the Triangle Midsegment Theorem for midsegment DF where F is the midpoint of OC B 2q 2r D E A 0 0 0 C 2p 0 x The midpoint of OC is and BC F P 0 F p 0 F p 0 DF Because DF BC F 0 p Because the slopes of DF and BC are both equal to P 9 BC DF r P 9 r p q 1 1 20 p 2pq q p