5.2.4.38 Various Problems on the Plane

\ (\ underline {\ mathrm {y} _ {\ text {Sliding:}}} \) The straight line passing through the middle of the diagonals of the quadrangle forms the angles \ (50^{\ circ} \) and \ (80 \ circ} {\ circ} \). Prove that the distance between the middle of the diagonals is half of one of the sides of the quadrangle.