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Polygons Where has Polly gone?

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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.

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**Circle the figures that are polygons:**

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**Why are these NOT polygons?**

A. Open side B. Curved side C. Vertex has more than 2 segments that meet D. Curved side B C D

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**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

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**List all the diagonals in this polygon:**

DB DA EC EB AC E B C D

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**Polygons are named by the number of sides.**

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**Name these polygons: A E B C F D A. triangle B. Quadrilateral**

C. Pentagon D. Hexagon E. Octagon F. Dodecagon E B C F D

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**Polygons with all sides and angles equal are regular polygons**

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

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**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

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**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.

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**Now, tear off the three angles of the triangle**

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

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**What is the measure of a straight line?**

180

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**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° ے1

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**The sum of the angles of any triangle is 180°**

Find the measure of the missing angle: ے2 = ( ) ے2 = (130) ے2 = 50° ے2 65° 65°

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**Find x: 3x - 4 + 5x + 10 + 6x + 6 = 180 14x + 12 = 180 -12 -12**

14x = 168 x = 12

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**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 What is the sum of the angles of this quadrilateral? 2 x 180° = 360°

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**What is the sum of the angles in this hexagon?**

720°

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**What is the sum of the angles in this pentagon?**

3 x 180° = 540°

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**Do you HAVE to draw the triangles to find out how many of them there are in a polygon?**

NO! 4 sides, 5 sides, sides, 2 triangles triangles triangles n sides, n-2 triangles!

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**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°

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**Find the missing angle measure in this polygon:**

180(5-2) = 180(3) = 540° 540° = X 540 = X 116° = X

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**Find the missing angle measure in this polygon:**

180(9-2) = 180(7) = 1260° 1260° = X 1260 = X 121° = X

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**raise your achievement**

practice will raise your achievement The End

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P O L Y G O N S 2-6. DEFINITION A POLYGON is the union of segments in the same plane such that each segment intersects exactly two others at their endpoints.

P O L Y G O N S 2-6. DEFINITION A POLYGON is the union of segments in the same plane such that each segment intersects exactly two others at their endpoints.

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