SOLUTION: Prove the theorem that states that if AD/DB=AE/EC, then DE||BC

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Question 1019001: Prove the theorem that states that if AD/DB=AE/EC, then DE||BC
Answer by ikleyn(52780) About Me  (Show Source):
You can put this solution on YOUR website!
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Prove the theorem that states that if AD/DB=AE/EC, then DE||BC
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The Theorem formulation is as follows:


   If in a triangle a straight line connects two sides and cuts off proportional segments in the triangle sides, 
   then this straight line is parallel to the third side of the triangle. 


See the lesson In a triangle a straight line parallel to its side cuts off a similar triangle in this site, Theorem 2.