# Trapezoid

## Trapezoid

Quadrilateral with at least one pair of parallel sides.

### Properties

The parallel sides of a trapezoid are called the bases of the trapezoid. In the general case, in which the quadrilateral has only one pair of parallel sides, the sides are called the short base and the long base.

Based on its properties, a trapezoid also belongs to the family of quadrilateral.

### Formula

The area A of a trapezoid whose bases are b and B and whose height is h is: $$A=\frac{(B +b) × h}{2}$$.

### Educational notes

The problem with definitions is that students often have a tendency to limit their meaning, rather than understand them from a general perspective.

For example, a quadrilateral with a pair of parallel sides is called a “trapezoid,” but that does not mean that a trapezoid can only have one pair of parallel sides. For this reason, “at least one pair of parallel sides” is specified. As a result, all parallelograms are trapezoids. If the definition were to be understood in the strictest sense, then a quadrilateral with more than one pair of parallel sides would no longer have just one pair and would not be a trapezoid!