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midsection of a trapezoid
The midsection of a trapezoid.( also called the median) is created by drawing a line from the midpoint of one leg to the midpoint of the other leg.

The length of the midsection can be calculated by adding the length of the two bases and dividing by two.

Midsection EF = AB + DC /2

isosceles triangle with congruent base angles
A trapezoid can have a right angle
The base angles of an Isosceles trapezoid are congruent and opposite angles are supplementary.
∠A and ∠B and ∠D and ∠C are congruent
∠A and ∠C and ∠B and ∠D are supplementary

The angles formed by the legs on the same side of a trapezoid are adjacent angles, and are supplementary. (add to 180 degrees)

∠A and ∠D and ∠B and ∠C are adjacent and supplementary

angles of a trapezoid
  • A trapezoid is a quadrilateral with exactly one pair of parallel sides.
  • The parallel sides of a trapezoid create the bases.
  • The sum of the interior angles of a trapezoid equals 360 degrees, and the angles on each side of the trapezoid are supplementary.
  • A trapezoid has four vertices, also called corners.
  • The median of a trapezoid is a line that connects the midpoint of the two legs.
  • A trapezoid has one pair of parallel sides. A parallelogram has two pairs of parallel sides.
  • In addition there are right trapezoids and an isosceles trapezoid. 
  • An isosceles trapezoid is a trapezoid with two parallel sides, and the two other sides are congruent.
  • In addition the diagonals of an isosceles triangle are congruent.
  • The base angles of an isosceles trapezoid are congruent.
  • A right trapezoid has two right angles.
  • In the UK a trapezoid is called a trapezium
common core standard
Common Core Standard

A trapezoid is a quadrilateral.









A trapezoid has two parallel sides, and two non-parallel sides.








The interior angles of a trapezoid add to 360 degrees, and the angles on each side are supplementary.









Area formula of a trapezoid equals


Area  = 1/2 (b1+b2) h  


h = height

b = base







Perimeter formula of a trapezoid equals


Perimeter = b1 +b2+s1+s2








Height of a Trapezoid

h= z * SinB or h =w * SinA



Diagonals length






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video tutorial area of a parallelogram

Properties of a Trapezoid

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Formula for finding the perimeter of a trapezoid

Step by step directions for finding the perimeter
trapezoid 2 non- parallel sides
trapezoid with angles of 110 and 70 degrees
trapezoid with bases labeled
height of trapezoid
d=square root of a^2 + b^2 -2xaxbxcos(B)
formula diagonal length of a trapezoid
diagonal length trapezoid
trapezoid labeled a,b,c.d and height
trapezoid with 18 unit base, 4 unit sides,10 unit top
check answer
Video works out height problem

What is the height of an isosceles trapezoid with bases of 10 and 18 units, a side length of 4 units, and an angle measure of 50 degrees? (see picture)

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The Interior angles of a trapezoid add to 360 degrees.

Angles of a Trapezoid