Theorem: The segment joining the midpoints of two sides of a triangle is parallel to the third side and half its length.
A two-column proof of the theorem is shown, but the proof is incomplete.

http://prntscr.com/9492vo

Incomplete proof: http://prntscr.com/9492zx

Which of the following completes the proof?
By definition of congruence
Converse of corresponding angles postulate
By substitution
By construction

Question

Theorem: The segment joining the midpoints of two sides of a triangle is parallel to the third side and half its length.
A two-column proof of the theorem is shown, but the proof is incomplete.

http://prntscr.com/9492vo

Incomplete proof: http://prntscr.com/9492zx

Which of the following completes the proof?
 By definition of congruence
 Converse of corresponding angles postulate
 By substitution
 By construction

leahhhmorgannn · Answer

@ganeshie8 would this be "by substitution"?

leahhhmorgannn · Answer

@Directrix

directrix · Answer

Of the options, the only one I see that might be correct is  By substitution although I don't feel that it fits in the proof.

leahhhmorgannn · Answer

I didn't feel like it fit exactly, but it did seem like the only one that was right. 
Thanks.

directrix · Answer

You are welcome.