Question

what is the missing step in this proof?

(A)Statement: The slope of  The slope of 

Reason: Definition of the slope.

(B)Statement: The slope of  The slope of 

Reason: Transitive property of equality.

(C)Statement:  

Reason: Corresponding sides of congruent triangles are congruent.

(D)Statement: 

Reason: ASA(angle-side -angle).

Done

Given: ΔABC (view diagram )
Prove: A midsegment of ΔABC is parallel to a side of ΔABC.

Statement Reason
(Steps 1−5)
6. AC ∣∣∣∣ DE definition of parallel lines
7. Let F be the midpoint of AC¯¯¯¯¯. defining a midpoint
8. F=(x1+x32,y1+y32) definition of midpoint
9. slope of DF = y1+y32−y1+y22x1+x32−x1+x22 = y3−y2x3−x2
the slope of BC = y3−y2x3−x2 definition of slope
10.
11. DF ∣∣∣∣ BC definition of parallel lines
12. Similarly, EF is parallel to AB. steps similar to steps 1−11