properties of parallelogram

The key properties of a parallelogram are:

- Opposite sides are parallel
- Opposite sides are congruent
- Opposite angles are congruent
- Any two consecutive angles are supplementary (add up to 180 degrees)
- The two diagonals bisect each other

To find the perimeter of a parallelogram, add up the four side lengths.

To find the area of a parallelogram, multiply base * height. Note that the height must be measured perpendicular to the base.

A rectangle and a square are special cases of parallelograms, where all four angles are right angles. A rhombus and a square are special cases of parallelograms, where all four side lengths are the same.

## Comments

Some additional points about the five listed properties. The first one is the definition of a parallelogram. The other four are theorems that can each be proven with a two-column proof.