Robin English
Concept Card
Not Trapezoids
Special Cases
of Trapezoids
Trapezoid
Figure 1
Isosceles Trapezoid
Figure 2
Key
CCoonncceepptt Q
Quueessttiioonnss
T
Trraappeezzooiidd FFaaccttss





Same Length
A trapezoid is a four sided shape
(quadrilateral) and has at least one
pair of parallel sides (figures 1 & 2).
It can be called an isosceles
trapezoid (figure 2) if the sides that
aren’t parallel are equal in length and
angles from coming from a parallel
side are equal (a=b & c=d).
The two parallel lines are called bases
and the two non parallel lines are
called the legs (figure 2).
All the interior angles of a trapezoid
always add up to 360 degrees.
The angles on the same leg of the
trapezoid are called supplementary
angles because they add up to 180
degrees. See the trapezoid model
(figure 1) where angle NML and angle
MLO equal 180 degrees.


Same Angle
Parallel Sides



180°


360°
Angle Degrees

Can you name the other shapes in the
shaded box above? (rhombus,
rectangle, circle, parallelogram,
triangle, kite, square)
If a four sided shape is also called a
quadrilateral, which shapes are called
quadrilaterals like the trapezoid?
What other shapes have at least one
pair of parallel lines? Which ones
have two sets of parallel lines?
What other shapes have equal angles
coming from parallel sides?
What shape(s) above has a total of
180 degrees?
What shape(s) above also have 360
degrees?
Why do you think there are special
cases of trapezoids? What do those
shapes have in common with a
trapezoid? Why is there only one four
sided shape that is not considered a
special case of a trapezoid?