Access full lesson containing this video at: http://www.yourteacher.com/geometry/parallelogram.php Students learn the definition of a parallelogram, which states that if a quadrilateral is a parallelogram, then opposite sides are parallel. Students also learn the following theorems related to parallelograms. If a quadrilateral is a parallelogram, then opposite sides are congruent. If a quadrilateral is a parallelogram, then opposite angles are congruent. If a quadrilateral is a parallelogram, then the diagonals bisect each other. Students are then asked to solve problems related to the properties of parallelograms using Algebra. (less info)