Khan Academy on a Stick
Proof: Diagonals of a parallelogram bisect each other
Proving that a quadrilateral is a parallelogram if and only if its diagonals bisect each other
If the above player doesn't work, try this direct link.
Proving that a quadrilateral is a parallelogram if and only if its diagonals bisect each other
If the above player doesn't work, try this direct link.