Trapezoid (USA definition)
From Greek: trapeze, -oid -"like"
A quadrilateral which has one pair of parallel sides
(but see definition notes below)
Try this Drag the orange dots on each vertex
to reshape the figure. Notice that the sides AB and CD remain parallel.
(If there is no image below, see support page.)
Attributes
| Base |
One of the parallel sides. Every trapezoid has two bases.
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| Leg |
The non-parallel sides are legs. Every trapezoid has two legs.
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| Altitude |
The altitude of a trapezoid is the
perpendicular distance from one base to the other.
(One base may need to be extended).
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| Median |
The median
of a trapezoid is a line joining the midpoints of the two legs. See Trapezoid median
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| Area |
The usual way to calculate the area is the average base length times altitude.
See Area of a Trapezoid
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| Perimeter |
The distance a round the trapezoid. The sum of its side lengths.
See Perimeter of a Trapezoid
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If both legs are the same length, this is called an isosceles trapezoid, and both base angles are the same.
If the legs are parallel, it now has two pairs of parallel sides, and is a parallelogram.
Definition notes
There is considerable confusion over the definition of 'trapezoid' and 'trapezium' due to differences in the British and US versions.
As you can see from the table below, the meanings of the two words are exactly reversed between the US and British interpretations.
| |
British |
USA |
| Trapezoid |
A quadrilateral with no sides parallel |
A quadrilateral with one pair of parallel sides |
| Trapezium |
A quadrilateral with one pair of parallel sides |
A quadrilateral with no sides parallel |
For the definition of trapezium see Trapezium
Related polygon topics
General
Types of polygon
Area of various polygon types
Perimeter of various polygon types
Angles associated with polygons
Named polygons
(C) 2007 Copyright John Page
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