Classifying Quadrilaterals “…geometric shapes are the alphabet in which the book of nature is written." -Galileo

What is a Quadrilateral?  A quadrilateral is a two-dimensional figure formed by connecting four segments endpoint to endpoint with each segment intersecting exactly two others. It also has four sides and four angles.

What is a Quadrilateral?  Look around you, do you see shapes that could be termed a quadrilateral?  Take about two minutes to draw five different shapes that you think could be classified as a quadrilateral.

Types of Quadrilaterals  Trapezoid  Parallelogram  Square  Rectangle  Kite, Dart  Rhombus  Rectangle

Copyright © 2000 by Monica Yuskaitis Quadrilateral Family parallelogram rectangle rhombus square trapezoid

Classification of Quadrilaterals  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.

Name that Quadrilateral!  A square is a quadrilateral with all sides and angles equal.  If all quadrilaterals have 360 o total, what is the angle of each vertex in a square?

Name that Quadrilateral!  A quadrilateral with all angles equal is a rectangle.  A quadrilateral with all sides equal is a rhombus.

 A quadrilateral with at least one pair of parallel sides is a trapezoid. Name that Quadrilateral!

 A quadrilateral with both pairs of opposite sides parallel and equal in length is known as a parallelogram.  Parallelograms can be considered special cases of trapezoids, since they have a least one pair of parallel sides.

Name that Quadrilateral!  A quadrilateral with two separate pairs of equal adjacent sides is commonly called a kite.  However, if the kite is concave, a dart is a more appropriate term.

 Examples of shapes or curves that are not classified as quadrilaterals. They do not follow the definition of a quadrilateral. Can you give a reason why? Are They Quadrilaterals? A C B