Answer:
Missing part is
Slope of DF = Slope of BC
Reason:Transition property of equality
Explanation:
Given:
Proof for a midsegment of triangle ABC is parallel to a side of triangle ABC
In the step by step explanation,
A,B, C are asumed to have vertices (x1,y1)(x2,y2) and (x3,y3)
D and F are defined as mid points.
Coordinates of D and F are found out using mid point formula.
Then slope of BC and slope of DF are found out using two point formula for straight lines.
All these were done correctly.
The missing part is to state that
Slope of DF =Slope of BC (Reason:Transition property of equality)
Next step is done rightly as DF parallel to BC