Definition and Parts of a Trapezoid
Definition and parts of a trapezoid is a Grade 6 geometry concept from Reveal Math, Course 1. A trapezoid is a quadrilateral with exactly one pair of parallel sides, called the bases (b₁ and b₂). The non-parallel sides are called legs. The height of a trapezoid is the perpendicular distance between the two bases — not the length of a leg. Understanding the vocabulary and structure of a trapezoid is the prerequisite for applying the area formula A = 1/2 × (b₁ + b₂) × h, which students encounter later in the same unit.
Key Concepts
Property A trapezoid is a four sided shape (quadrilateral) with exactly one pair of parallel sides. Bases ($b 1$ and $b 2$): The two parallel sides. They are usually different lengths. Height ($h$): The straight, perpendicular distance between the two bases.
Examples A trapezoid has a top base of 6 inches and a bottom base of 10 inches. Its height is the straight 5 inch line connecting them, not the slanted sides on the edges. A right trapezoid has one straight side that forms a 90° angle with the bases. In this case, that straight side is the height!
Explanation Think of a trapezoid as a triangle that had its top chopped off perfectly straight! The most important rule is identifying the bases and the height. The bases are the two lines that will never touch, no matter how far you draw them. The height is the straight up distance between those bases, always forming a perfect right angle.
Common Questions
What is a trapezoid in math?
A trapezoid is a quadrilateral with exactly one pair of parallel sides. The parallel sides are called bases (labeled b₁ and b₂), and the non-parallel sides are called legs. A right trapezoid has one right angle; an isosceles trapezoid has equal-length legs.
What are the parts of a trapezoid?
The parts are: two bases (the parallel sides, often labeled b₁ and b₂), two legs (the non-parallel sides), and the height h (the perpendicular distance between the bases). The height is always measured at a right angle to the bases.
What is the height of a trapezoid?
The height of a trapezoid is the perpendicular distance between the two bases — measured straight across, at 90° to both bases. It is not the length of either leg unless the trapezoid has a right angle.
Is a parallelogram a trapezoid?
It depends on the definition used. The exclusive definition (exactly one pair of parallel sides) says no — a parallelogram is not a trapezoid. The inclusive definition (at least one pair) says yes. Most US 6th grade curricula, including Reveal Math, use the exclusive definition.
What is the difference between a trapezoid and a parallelogram?
A parallelogram has two pairs of parallel sides. A trapezoid (exclusive definition) has exactly one pair of parallel sides. Rectangles, squares, and rhombuses are all parallelograms; trapezoids are a different category.
When do students learn about trapezoids?
Trapezoids and their properties are introduced in Grade 6 in Reveal Math, Course 1, as part of the area of polygons unit. Students use the definition to apply the trapezoid area formula.
Which textbook covers the definition and parts of a trapezoid?
This concept is in Reveal Math, Course 1, used in Grade 6 math. It is covered in the area chapter alongside other polygon types.