Group Assignment:
Due Monday 10/11 at
Definition: A quadrilateral is a parallelogram if the opposite sides are parallel.
Prove
that each of the following conditions is true if and only if the quadrilateral
is a parallelogram. In other words, any
one of the following statements is equivalent to the definition.
1.
The opposite
sides of a quadrilateral are congruent.
2.
The opposite
angles of a quadrilateral are congruent.
3.
The diagonals of
the quadrilateral bisect each other. (This means that the point of intersection of the
diagonals is the midpoint of each diagonal.)
4. Two sides of the quadrilateral are congruent and parallel.