### POLYGON

Transcript: INTRODUCTION TO POLYGON INTRODUCTION TO POLYGON IS IT A POLYGON? IS IT A POLYGON? Polygons are 2-dimensional shapes. They are made of straight lines, and the shape is "closed" (all the lines connect up). Polygon (straight sides) Not a Polygon (has a curve) Not a Polygon (open, not closed) POLYGON POLYGON DEFINITION DEFINITION Polygon comes from Greek. Poly- means "many" and -gon means "angle" Pictures Pictures TYPES OF POLYGON TYPES OF POLYGON A. CONCAVE AND CONVEX B. SIMPLE AND COMPLEX C. REGULAR AND IRREGULAR A. CONCAVE & CONVEX A. CONCAVE & CONVEX A convex polygon has no angles pointing inwards. More precisely, no internal angle can be more than 180°. If any internal angle is greater than 180° then the polygon is concave. (Think: concave has a "cave" in it) CONVEX CONVEX CONCAVE CONCAVE B. SIMPLE & COMPLEX B. SIMPLE & COMPLEX A simple polygon has only one boundary, and it doesn't cross over itself. A complex polygon intersects itself! Many rules about polygons don't work when it is complex. SIMPLE SIMPLE COMPLEX COMPLEX C.REGULAR & IRREGULAR C.REGULAR & IRREGULAR A regular polygon has all angles equal and all sides equal, otherwise it is irregular REGULAR REGULAR IRREGULAR IRREGULAR MORE EXAMPLE MORE EXAMPLE Irregular Hexagon Concave Octagon Complex Polygon (a "star polygon", in this case a pentagram) Names of Polygons Names of Polygons A triangle has three sides and three angles Triangles Triangles A Quadrilateral has four-sides, it is 2-dimensional (a flat shape), closed (the lines join up), and has straight sides. Quadrilaterals Quadrilaterals A pentagon is a 5-sided Polygon (a flat shape with straight sides): Pentagon Pentagon hexagon is a 6-sided polygon (a flat shape with straight sides). Hexagon Hexagon An octagon is an 8-sided polygon (a flat shape with straight sides). First, have a play with an octagon: Octagon Octagon Nonagon (or Enneagon) Nonagon (or Enneagon) Decagon Decagon BSEDUCATION MATHEMATICS LACSON, JR. ABELARD C. THANK YOU!! https://www.mathsisfun.com/geometry/polygons.html THANK YOU!! https://www.mathsisfun.com/geometry/polygons.html