Question

Prove that a lie divides two sides of a triangle proportionally is parallel to the third side. Be sure to create and name the appropriate geometric figures.

Answer 1

Congruence between two triangles means six items, all three sides and all three angles, are congruent. Thus the statement ABC DEF has a very precise meaning. It succinctly summarizes the six statements (assume lines atop these segments): ABDE, BCEF, ACDF, AD, BE, and CF. It is very important to maintain the vertices in the proper order. Not doing so is a common mistake.