Lesson-16-Angle-sum-of-Polygons with activity

sharing here another ppt for reference for angle sum of polygons, from the respective owner

1. Be Ready… 1) Write down the name of following polygons 2) Find the missing angle   3) Find the missing angle   4) What is the name of the polygon with seven sides?

2. 1) Write down the name of following polygons 2) Find the missing angle   3) Find the missing angle   4) What is the name of the polygon with seven sides? Triangle Square Pentagon Hexagon Octagon C=180-(38+85) C=57       Be Ready…

3. A polygon is a two-dimensional shape with straight sides. Vocabulary check A polygon is regular when all angles are equal and all sides are equal. Irregular Polygons Regular: Polygon:

4. Interior Angle Sum of Polygons Name of polygon Number of sides Number of triangles inside polygon Sum of interior angles Triangle Quadrilateral Pentagon Hexagon Heptagon Octagon

5. How many triangles?

6. Name of polygon Number of sides Number of triangles inside polygon Sum of interior angles Triangle Quadrilateral Pentagon Hexagon Heptagon Octagon 3 1 x 180 1 180

7. 2 x 180 = 360° Angles in a quadrilateral always add up to 360 ° 180° 180° 180° 180° How many triangles make up a quadrilateral?

8. Name of polygon Number of sides Number of triangles inside polygon Sum of interior angles Triangle Quadrilateral Pentagon Hexagon Heptagon Octagon 3 1 x 180 1 180 4 2 2 x 180 360

9. Find the angle sum of a pentagon by splitting into as few triangles as possible. 180° 180° 180° 3 x 180° = 540° Angles in a pentagon always add up to 540 ° In pairs, do the same with the pentagon, hexagon, heptagon and octagon Make sure you start splitting the polygon up from the same vertex.

10. Name of polygon Number of sides Number of triangles inside polygon Sum of interior angles Triangle Quadrilateral Pentagon Hexagon Heptagon Octagon 3 1 x 180 1 180 4 2 2 x 180 360 5 3 3 x 180 540 6 4 4 x 180 720 7 5 5 x 180 900 8 6 6 x 180 1080

11. Triangle Quadrilateral Pentagon Hexagon 1 triangle So far… Interior angle sum of polygons 2 triangles 3 triangles 4 triangles Sides Triangles Sum of interior angles Can you spot the connection between the number of sides and the sum of the interior angles? number of sides Sum of interior angles What is the interior angle sum of an n-sided shape? Interior Angle Sum of Polygons (n)

12. Interior Angle Sum of Polygons Find the missing angle Interior angle sum of a pentagon = (5 - 2 ) x 180 = 3 x 180 = 540 Missing angle x = 540 – ( 68 + 121 + 103 + 85 ) = 540 - 377 = 163 Sum of interior angles in n-sided polygon = (n – 2) × 180 Where n is the number of sides Step 1: Find the interior angle sum of pentagon Step 2: Interior angle sum –total of other angles

13. Find the interior angle sum in a 12 sided polygon . Find the missing angles a) c) b) Hint: First, find the interior angle sum. Your turn Sum of interior angles in n-sided polygon = (n – 2) × 180 Where n is the number of sides

14. Find the interior angle sum in a 12 sided polygon. Find the missing angles a) 76 c) b) 100 140 1800

15. To finish… Find the sum of interior angles of a 22-sided shape