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Polygons Where has Polly gone? Polygon  A closed figure formed by joining three or more segments in a plane at their endpoints, with each line segment.

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Presentation on theme: "Polygons Where has Polly gone? Polygon  A closed figure formed by joining three or more segments in a plane at their endpoints, with each line segment."— Presentation transcript:

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2 Polygons Where has Polly gone?

3 Polygon  A closed figure formed by joining three or more segments in a plane at their endpoints, with each line segment joining exactly 2 others.  Each line segment is called a side of the polygon. This polygon has 8 sides.

4 Circle the figures that are polygons:

5 Why are these NOT polygons?  A. Open side  B. Curved side  C. Vertex has more than 2 segments that meet  D. Curved side

6 Vertex and diagonal  A vertex is where 2 sides meet.  A diagonal joins two nonconsecutive vertices.  Name the vertices and the diagonal in this polygon:  Vertices: A,B,C,D,E,F  Diagonal: CE

7 List all the diagonals in this polygon:  DB  DA  EC  EB  AC

8 Polygons are named by the number of sides.

9 Name these polygons:  A. triangle  B. Quadrilateral  C. Pentagon  D. Hexagon  E. Octagon  F. Dodecagon

10 Polygons with all sides and angles equal are regular polygons. Circle the regular polygons:

11 Polygons are named by naming consecutive vertices in order.  Circle all the correct names for this polygon: pentagon ABCDE pentagon AEDCB pentagon ACDBE pentagon DCBAE pentagon BDCAE pentagon BAEDC

12 What is the sum of the angle measures in a triangle?  Please draw a triangle on a piece of scratch paper. It can be any size or shape, just be sure it is a triangle.

13  Now, tear off the three angles of the triangle. Position the angles side-by-side on your desk. What shape do they make? Draw the angles side-by-side on your paper like this ↑

14 What is the measure of a straight line?

15 The sum of the angles of any triangle is 180°  Find the measure of the missing angle:  ے1 = (90 +35)  ے1 = (125)  ے1 = 55° 35° 90° ے1ے1

16 The sum of the angles of any triangle is 180°  Find the measure of the missing angle:  ے2 = ( )  ے2 = (130)  ے2 = 50° 65° ے2ے2

17 Find x:  3x x x + 6 = 180  14x + 12 = 180   14x = 168  x = 12

18 What is the sum of the angle measures in a polygon?  We can divide the polygon into triangles, then multiply the number of triangles by 180°  How many triangles make up this quadrilateral? 2222  What is the sum of the angles of this quadrilateral?  2 x 180° = 360°

19 What is the sum of the angles in this hexagon?  4 x 180° =  720°

20 What is the sum of the angles in this pentagon?  3 x 180° =  540°

21 Do you HAVE to draw the triangles to find out how many of them there are in a polygon?  NO! 4 sides,5 sides, 6 sides, 2 triangles 3 triangles 4 triangles n sides, n-2 triangles!

22 What is the sum of the measures of the angles of these polygons? 180(6-2)180(8-2)180(10-2) = 180(4)=180(6)= 180(8) = 720°= 1080°=1440°

23 Find the missing angle measure in this polygon:  180(5-2)  = 180(3)  = 540°  540° = X  540 = X  116° = X

24 Find the missing angle measure in this polygon:  180(9-2)  = 180(7)  = 1260°  1260° = X  1260 = X  121° = X

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