3. A quadrilateral is a polygon
with four sides (or 'edges') and
four vertices or corners.
Sometimes, the term quadrangle
is used, by analogy with
triangle, and sometimes
tetragon for consistency with
pentagon (5-sided), hexagon(6-
sided) and so on. The word
quadrilateral is made of the
words quad (meaning "four")
and lateral (meaning "of
sides").
4. “…geometric shapes are the
alphabet in which the book of
nature is written." –Galileo
A concave
quadrilateral
contains at least one
angle that is >180 o .
A quadrilateral is
convex if each
vertex lies in the
interior of the
opposite angle.
5. Q.Look around you, do you see shapes that could
be termed a quadrilateral? Take about two
minutes to think and classify the things as
quadrilaterals around you.
A. Television , Door , Photo frame , Laptop and
Table.
7. A rectangle is a
four-sided shape
where every A square has
angle is a equal sides and
right angle every angle is a
(90°). right angle
Also opposite (90°)
sides are parallel Also opposite
and of equal sides are
length. parallel.
8. A rhombus is a four- Trapezoid (called a
trapezium in the UK) has
sided shape where all
one pair of opposite sides
sides have equal length.
parallel.
Also opposite sides are It is called an Isosceles
parallel and opposite trapezoid if the sides that
angles are equal. aren't parallel are equal
Another interesting in length and both angles
thing is that the coming from a parallel
diagonals (dashed lines side are equal, as shown.
in second figure) of a Language Note: In the US
rhombus bisect each a "trapezium" is a
other at right angles. quadrilateral with NO
parallel sides
9. It looks like a kite. It has two
pairs of sides. Each pair is
Opposite sides are made up of adjacent sides
parallel and equal in that are equal in length. The
length, and opposite angles are equal where the
pairs meet. Diagonals
angles are equal
(dashed lines) meet at a right
(angles "a" are the angle, and one of the
same, and angles "b" diagonal bisects (cuts equally
are the same). in half) the other.
... and that's it for the special
quadrilaterals.
10. The goal is to know and apply the properties of quadrilaterals. (EX :
I)
11. The goal is to know and apply the properties of quadrilaterals. (EX
:II)
12. A B C
Examples of shapes or curves that are not
classified as quadrilaterals. They do not follow
the definition of a quadrilateral. But why?
A) It crosses over itself intersecting more then
two segments
B) There are four sides, but the segments are not
straight
C) Same as B.
