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Slideshow 33, Mathematics Mr Richard Sasaki, Room 307. Polygons and Internal Angle Properties. Objectives. Recall the sum of interior angles in a triangle Find the number of interior angles in any polygon. The Triangle. How about other shapes?.
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Slideshow 33, Mathematics Mr Richard Sasaki, Room 307 Polygons and InternalAngle Properties
Objectives • Recall the sum of interior angles in a triangle • Find the number of interior angles in any polygon
The Triangle How about other shapes? Do you remember the sum of interior angles in a triangle? (What’s the total number of degrees of all three angles in the triangle?) There is always 1800. A long time ago, you might have proved it by doing this… Remember? Angles on a line add up to 1800.
Shape Names – You need to know these! 4 5 3 Triangle Quadrilateral Pentagon 7 6 8 Hexagon Septagon / Heptagon Octagon 9 Nonagon Decagon 10
Interior Angles An easy way to find out a shape’s sum of interior angles is by splitting the shape into a minimum number of triangles. For example, a pentagon can split into three triangles. Each triangle contains 1800 so the pentagon contains 1800x 3 = 5400. The shape’s number of interior angles is equal to the number of triangles x 1800.
Interior Angles Hopefully you found out the following… So… The Sum of Interior Angles = (# of sides – 2) x 1800.