# Polygons

**Polygon: **A simple closed curve made up of only line segments is called a polygon.

**Classification of polygons:**

Number of Sides |
Classification |

3 | Triangle |

4 | Quadrilateral |

5 | Pentagon |

6 | Hexagon |

7 | Heptagon |

8 | Octagon |

9 | Nonagon |

10 | Decagon |

... | ... |

n | n-gon |

**Diagonal**: A diagonal is a line segment connecting two non-consecutive vertices of a polygon.

**Convex polygons: **Where all the interior angles are less than 180° and no part of its diagonals lie outside the polygon.

**Concave polygons:** Where at least one interior angle is more than 180° and some of the diagonals will lie outside the polygon.

**Regular polygons:** A regular polygon is both 'equiangular' and 'equilateral'. e.g. equilateral triangle.

**Irregular polygons:** Polygons which are not equiangular or equilateral are irregular polygons. e.g. right-angled triangle.

**Angle sum property: **Sum of all interior angles = \( (n - 2) \times 180° \) where n --> number of interior angles.