Find the length of the midsegment of trapezoid ABCD . A trapezoid A B C D, shortest side D C is the base, sides D C labeled 13 and A B labeled 39 are parallel. A line segment from the mid points of A D and B C is parallel to both sides A B and D C. Side A D is divided into two parts marked with single tick marks and side B C is divided into two parts marked with double tick marks. The length of the midsegment is