Here is the list of theorems that are important for this chapter.

• A diagonal of a parallelogram divides it into two congruent triangles.

• Opposite sides of a parallelogram are equal.

• Opposite angles of a parallelogram are equal.

• Diagonals of a parallelogram bisect each other.

• A quadrilateral is a parallelogram if opposite sides/angles are equal or if its diagonals bisect each other.