In the previous geometric construction, vertices E and F are midpoints. Change the position of vertices B or C. Observe the measurements of segments BC, AD and EF. Can you notice some relation between the measurement of segment EF and the other two segments?
If a line segment joins the midpoints of the non-parallel sides of a trapezoid, then: [list][*]It is parallel to the bases; [/*][*]It is equal to one half the sum of the bases.[/*][/list]