Prove that the st. lines joining the mid pts of the opposite sides of aquadrilateral bisect each other.
MID PTS THEOREM
let ABCD be a parallelogram.
E,F,G,H be the mid points of the sides AB,BC,CD,DA.
EH II BD...
EH =1/2[BD]....mid pt thm
FG II BD and FG=1/2[BD]
EH II FG
EFGH is a parallelogram....one pair of opp sides is parallel and equal
so FH and EG become the diagonals of this parallelogram, so they must bisect each other.