<Ul> <Li> The diagonals have the same length . </Li> <Li> The base angles have the same measure . </Li> <Li> The segment that joins the midpoints of the parallel sides is perpendicular to them . </Li> <Li> Opposite angles are supplementary, which in turn implies that isosceles trapezoids are cyclic quadrilaterals . </Li> <Li> The diagonals divide each other into segments with lengths that are pairwise equal; in terms of the picture below, AE = DE, BE = CE (and AE ≠ CE if one wishes to exclude rectangles). </Li> </Ul> <Li> The diagonals have the same length . </Li> <Li> The base angles have the same measure . </Li> <Li> The segment that joins the midpoints of the parallel sides is perpendicular to them . </Li>

Properties of the diagonals of an isosceles trapezoid