Geometry Course/Polygon/Quadrilateral/Trapezoid

A Trapezoid (American English) or Trapezium (British English) is a quadrilateral that has two parallel sides and two non parallel sides. Some properties of trapezoids: The interior angles sum to 360° as in any quadrilateral. The parallel sides are unequal. Each of the parallel sides is called a base (b) of the trapezoid. The two angles that join one base are called 'base angles'. If the two non-parallel sides are equal, the trapezoid is called an isosceles trapezoid. In an isosceles trapezoid, each pair of base angles are equal. If one pair of base angles of a trapezoid are equal, the trapezoid is isosceles. A line segment connecting the midpoints of the non-parallel sides is called the median (m) of the trapeziod. The median of a trapezoid is equal to one half the sum of the bases (called b1 and b2). A line segment perpendicular to the bases is called an altitude (h) of the trapezoid. The area (A) of a trapezoid is equal to the product of an altitude and the median. Recall though that the median is half of the sum of the bases. Substituting for m, we get: