Polygons are 2-dimensional shapes which can exist in the Euclidean plane. They are made of straight lines, and the shape is "closed" (all the lines connect up).

### Types of Polygons

**Regular polygon:**A

**regular**polygon has all angles

**equal**and all sides

**equal**.

**Irregular polygon:**A

**irregular**polygon has all angles and sides

**equal**.

**Convex polygon:**A

**convex**polygon has all angles are less than

**180°**or no angles pointing inwards.

**Concave polygon:**If any internal angle is

**greater than 180°**then the polygon is

**concave**polygon.

**Simple polygon:**A

**simple**polygon has only one boundary, and it doesn't cross over itself.

**Complex polygon**: A

**complex**polygon intersects itself! Many rules about polygons don't work when it is complex.

### Names of Polygons

### General Maths on any Polygon

Interior Angle + Exterior Angle = 180°

Sum of Exterior Angle = 360°

Sum of Interior Angle = (n - 2) 180°

Diagonal of an n' sided polygon = n (n - 3)/2