Write these properties below the polygon shape. Write the word tricycle publicly. Ask : How many of you know what a tricycle is? How many wheels does a tricycle have? What do a tricycle and a triangle have in common? When students identify that a tricycle has three wheels and a triangle has three sides, make the connection between the prefix tri- and the number three.
See if any students have heard of other English words that begin with tri- and have three of something, for example triathlon, trio, trilogy, tripod, or trilingual. Below the properties of the triangle, write "Tri means 3. Ask : This shape is called a quadrilateral. What can you tell me about it? Direct students to identify a quadrilateral as a shape with four sides.
Some may also say that it has four angles. Continue by explaining that quad- means four. Students are unlikely to know many words that begin with quad- and have four of something, but you can show examples, such as quadruple, quadrant , or quadriceps which refers to a human muscle made up of four parts.
Write "quad means 4" below the quadrilateral. Pointing to the pentagon. Say : This is a pentagon. Students should identify the number of sides and possibly angles of a pentagon. Ask : Who knows what prefix means five in the word pentagon? Explain that in this case, penta- means five.
Students may be familiar with a pentathlon or the Pentagon building. Continue by introducing the hexagon and octagon. Some students will be thinking ahead and see that the prefixes for six and eight are hexa- and octa-.
Although in this lesson the prefixes are given with final vowels e. Lesson 2: Classifying Polygons Once your students can identify different polygons, move on to identifying properties of specific polygons. Say : We have talked about different kinds of polygons. How did we describe a triangle? List the properties of a triangle where all students can see: three-sided polygon, contains three angles or corners.
Say : Look at worksheet 1. All these figures are triangles, but some of them have special names. Look at figure c. Use your ruler to measure the three sides of this triangle. Kite : Two pairs of adjacent sides are of equal length; the shape has an axis of symmetry. Irregular Quadrilateral : a four-sided shape where no sides are equal in length and no internal angles are the same.
A six-sided shape is a hexagon, a seven-sided shape a heptagon, while an octagon has eight sides…. The names of polygons are derived from the prefixes of ancient Greek numbers.
The Greek numerical prefix occurs in many names of everyday objects and concepts. These can sometimes be useful in helping you remember how many sides a polygon has. For example:. There are names for many different types of polygons, and usually the number of sides is more important than the name of the shape.
A regular polygon has equal length sides with equal angles between each side. Any other polygon is an irregular polygon , which by definition has unequal length sides and unequal angles between sides. Circles and shapes that include curves are not polygons - a polygon, by definition, is made up of straight lines. See our pages on circles and curved shapes for more. The angles between the sides of shapes are important when defining and working with polygons.
See our page on Angles for more about how to measure angles. There is a useful formula for finding out the total or sum of internal angles for any polygon, that is:. Furthermore, if the shape is a regular polygon all angles and length of sides are equal then you can simply divide the sum of the internal angles by the number of sides to find each internal angle. As well as the number of sides and the angles between sides, the length of each side of shapes is also important.
Special Quadrilaterals. We can use a Venn diagram to help us group the types of quadrilaterals. A Venn diagram uses overlapping circles to show relationships between groups of objects. All "quadrilaterals" can be separated into three sub-groups: general quadrilaterals, parallelograms and trapezoids. Is a rectangle always a rhombus? No, because all four sides of a rectangle don't have to be equal.
We can put squares in the intersection of the two circles. From this diagram, you can see that a square is a quadrilateral, a parallelogram, a rectangle, and a rhombus! Is a trapezoid a parallelogram? Quadrilaterals can be classified by whether or not their sides, angles, diagonals, or vertices have special properties.
The classification schemes taught in elementary school involve the number of pairs of parallel sides, and the congruence of sides, and whether or not all the angles are right angles all angles are congruent.
The names of many of these special quadrilaterals are also typically part of the elementary curriculum, though little else about the properties of these figures may be studied until high school. Elementary school typically has children learn the names of. The square is also the name of the regular quadrilateral — one in which all sides are congruent and all angles are congruent.
Though the names that are given to individual figures does not change, the way that they are grouped may depend on the characteristics used to sort them. In the classification scheme below, rectangles F and B have the right hand column to themselves, but parallelograms are not grouped in a way that excludes A , which is not a parallelogram.
Children in primary grades often find it hard to assign anything geometrical or otherwise simultaneously to two categories. Similarly, students tend to treat rectangles and parallelograms as disjoint classes, rather than seeing a rectangle as a special type of parallelograms.
Another possible way to classify quadrilaterals is by examining their diagonals. This may be accessible for middle grade students who have learned about perpendicular lines and bisectors. Tesselation: The fact that the four vertices fit snugly around a single point allows us to arrange four copies of a quadrilateral around a point.
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