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8.7 Polygons

8.7 Polygons. I can identify regular and not regular polygons and find the angle measurements of regular polygons. Review The lengths of three sides of a triangle are given. Classify the triangle. 1. 12, 12, 12 2. 18, 10, 14 3. 15, 15, 26. equilateral. scalene. isosceles. Vocabulary.

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8.7 Polygons

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  1. 8.7 Polygons I can identify regular and not regular polygons and find the angle measurements of regular polygons

  2. Review The lengths of three sides of a triangle are given. Classify the triangle. 1. 12, 12, 12 2. 18, 10, 14 3. 15, 15, 26 equilateral scalene isosceles

  3. Vocabulary polygon regular polygon diagonal

  4. A polygon is a closed plane figure formed by three or more line segments. A regular polygon is a polygon in which all sides are congruent and all angles are congruent. Polygons are named by the number of their sides and angles.

  5. You can divide any quadrilateral into two triangles by drawing a diagonal, a line segment that connects two non-adjacent vertices. The sum of the interior angle measures in a triangle is 180°, so the sum of the interior angle measures in a quadrilateral is 360°.

  6. Tell whether each shape is a polygon. If so, give its name and tell whether it appears to be regular or not regular. not regular polygon pentagon

  7. Tell whether each shape is a polygon. If so, give its name and tell whether it appears to be regular or not regular. octagon regular polygon

  8. Tell whether each shape is a polygon. If so, give its name and tell whether it appears to be regular or not regular. regular quadrilateral

  9. Tell whether each shape is a polygon. If so, give its name and tell whether it appears to be regular or not regular. not regular quadrilateral

  10. Reading Math The prefixes in the names of the polygons tell you how many sides and angles there are. tri- = three quad- = four penta- = five hexa- = six octa- = eight 720°

  11. 1. Name each polygon and tell whether it appears to be regular or not regular. 2. What is the measure of each angle in a regular dodecagon (12-sided figure)? nonagon, regular; octagon, not regular 150°

  12. 1. Name the polygon and tell whether it appears to be regular or not regular. A. pentagon, not regular B. hexagon, regular C. heptagon, regular D. octagon, not regular

  13. 2. What is the measure of each angle in a regular decagon (10-sided figure)? A. 108 B. 144 C. 150 D. 140

  14. What is the exterior angle of a polygon? • What do the exterior angles of a regular polygon • add up to?

  15. Square The four angles create 360° 360 ÷ 4 = 90° Exterior angle is 90°

  16. REGULAR PENTAGON The five angles create 360° 360 ÷ 5 = 72° Exterior angle is 72°

  17. Angle facts about regular polygons Exterior angle = 360° ÷ number of angles

  18. EXERCISES Calculate the angles marked with letters 80° 66° 75° 100° 98° 91° B A 95° C 90° 85° 57° 25° 33°

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