we know that
The midsegment of a trapezoid is the segment connecting the midpoints of the two non-parallel sides of the trapezoid, and is parallel to the pair of parallel sides.
In this problem
the two non-parallel sides of the trapezoid are AD and BC
Step 1
Find the midpoint side AD
Let
E-------> the midpoint AD

Find the x-coordinate of the midpoint AD

Find the y-coordinate of the midpoint AD

the point E is equal to 
Step 2
Find the midpoint side BC
Let
F-------> the midpoint BC

Find the x-coordinate of the midpoint BC

Find the y-coordinate of the midpoint BC

the point F is equal to 
Step 3
Find the distance EF
we know that
The formula to calculate the distance between two points is equal to

we have

substitute the values


therefore
<u>the answer is</u>
the length of the midsegment of the trapezoid is 