Midsegments are lines that conect the midpoints of two sides of a triangle. This means that it divides both sides in two equal segments, for this diagram:
From this we can determine that segments AD and DB are equal.
So segment DB = 10
To calculate segment DF you have to apply the midsegment theorem that states that each midsegment is parallel to the third line (i.e. the side they dont intersect)
For this diagram: DE || AC and DF || BC
Next propperty you have to remember is that each midsegment is a halve of the third side, so for segment DF:
[tex]\begin{gathered} DF=\frac{1}{2}BC \\ DF=\frac{1}{2}26 \\ DF=13 \end{gathered}[/tex]
Segment DF=13
