Tom Q. answered • 09/06/12
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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.
Roman C.
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.
10/19/12