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Finding the Sum of a Polygon’s Interior Angles

7-Nov-14. Finding the Sum of a Polygon’s Interior Angles. The word ‘ poly gon ’ is a Greek word. Poly means many and gon means angles. Here are some polygons. Triangle. Pentagon. Octagon. How to find the sum of the interior angles – i.e. How to find a + b + c + d + e. b. a. c. d.

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Finding the Sum of a Polygon’s Interior Angles

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  1. 7-Nov-14 Finding the Sum of a Polygon’s Interior Angles The word ‘polygon’ is a Greek word. Poly means many and gon means angles. Here are some polygons Triangle Pentagon Octagon

  2. How to find the sum of the interior angles – i.e. How to find a + b + c + d + e b a c d e

  3. How to find the sum of the interior angles – i.e. How to find a + b + c + d + e Split the shape up into triangles

  4. How to find the sum of the interior angles – i.e. How to find a + b + c + d + e Split the shape up into triangles Each triangle contains 1800 1800 1800 1800

  5. How to find the sum of the interior angles – i.e. How to find a + b + c + d + e Split the shape up into triangles Each triangle contains 1800 3 x 180 = 5400 1800 1800 1800

  6. How to find the sum of the interior angles – i.e. How to find a + b + c + d + e Split the shape up into triangles Each triangle contains 1800 3 x 180 = 5400 The sum of the interior angles is 5400 1800 1800 1800

  7. Copy and complete this table. Find the interior angles by drawing and splitting up into triangles.

  8. Copy and complete this table. Find the interior angles by drawing and splitting up into triangles.

  9. Regular Polygons NB. If the polygon is regular, to find an interior angle use the rule: Interior Angle 1200 Int.Angle = 180 – (360 ÷ n) n is the number of sides Int. = 180 – (360 ÷ 6)  180 – 60 =120

  10. Regular Polygons exterior angle (180 – 120 = 60 NB. If the polygon is regular, to find an exterior angle use the rule: Interior Angle 1200 Ext.Angle = 360 ÷ n n is the number of sides And Ext. Angle = 180 – Int.Angle

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