Classifying Quadrilaterals “…geometric shapes are the alphabet in which the book of nature is written." -Galileo http://soundscapesinternational.com/sacred_geometry.php Next Slide Type your name and send:

Objectives Define what parallelograms, kites, rectangles, squares, rhombi, and trapezoids are. Sort and classify quadrilaterals. Determine which shapes are and are not quadrilaterals, given examples. Next Slide

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. www.dictionary.com A four sided polygon. Next Slide

Types of Quadrilaterals Trapezoid Parallelogram Square Rectangle Kite, Dart Rhombus Scalene Which one is NOT a quadrilateral? Next Slide

Classification of Quadrilaterals A concave quadrilateral contains at least one angle that is >180o. A quadrilateral is convex if each vertex lies in the interior of the opposite angle. www.cut-the-knot.org/Curriculum/Geometry/Quadrilaterals.shtml Next Slide

Name that Quadrilateral! (No points for this name!) A square is a quadrilateral with all sides and angles equal. If all quadrilaterals have 360o total, what is the angle of each vertex in a square? Ans: 90 degrees www.cut-the-knot.org/Curriculum/Geometry/Quadrilaterals.shtml Next Slide

Name that Quadrilateral! A quadrilateral with all angles equal is a rectangle. A quadrilateral with all sides equal is a rhombus. www.cut-the-knot.org/Curriculum/Geometry/Quadrilaterals.shtml Next Slide

In Euclidean geometry, a rhombus or rhomb is a convex quadrilateral whose four sides all have the same length. The rhombus is often called a diamond, after the diamonds suit in playing cards, or a lozenge, though the latter sometimes refers specifically to a rhombus with a 45° angle. Every rhombus is a parallelogram, and a rhombus with right angles is a square. (Euclid's original definition and some English dictionaries' definition of rhombus excludes squares, but modern mathematicians prefer the inclusive definition.)[1] The English word “rhombus” derives from the Ancient Greek ῥόμβος (rhombos), meaning spinning top. The plural of rhombus can be either rhombi or rhombuses. Next Slide

Name that Quadrilateral! Trapezoid A quadrilateral with at least one pair of parallel sides is a t……oid. Next Slide

Name that Quadrilateral! A quadrilateral with both pairs of opposite sides parallel and equal in length is known as a p….gram. www.cut-the-knot.org/Curriculum/Geometry/Quadrilaterals.shtml Parallelograms can be considered special cases of trapezoids, since they have a least one pair of parallel sides. Next Slide

Name that Quadrilateral! A quadrilateral with two separate pairs of equal adjacent sides is commonly called a ????. However, if the kite is concave, a dart is a more appropriate term. This is a dart: www.cut-the-knot.org/Curriculum/Geometry/Quadrilaterals.shtml Next Slide

Are They Quadrilaterals? C B 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? It crosses over itself intersecting more than two other segments. There are four sides, but the segments are not straight. Same as B. Next Slide

LO:To classify quadrilaterals I need more practice to help me understand this and I made lots of mistakes. B I am beginning to understand this and I got many of them correct. C I really understand this and I got most of them correct. Follow up activity

Work in pairs. You will be given the name of a shape Work in pairs. You will be given the name of a shape. For each shape, you must write as many facts as you can that are true about the shape in your book. For example you can say that a scalene triangle has three sides. You can not say that it does not have four sides. Last Slide