2. Polygons A Polygon is a closed plane figure formed by 3 or more segments Each segment intersects exactly 2 other segments only at their endpoints. No 2 segments with a common endpoint are collinear

3. Sides The segments that form a polygon are called its sides. In a polygon, no 2 segments with a common endpoint are collinear

4. Vertex of a Polygon The vertex of a polygon is the intersection of 2 of its sides.

5. EQUIANGULAR POLYGON An equiangular polygon is a polygon in which all angles are congruent

6. Equilateral Polygon An equilateral polygon is a polygon in which all sides are congruent.

7. REGULAR POLYGON If a polygon is both equiangular and equilateral, then it is called regular.

8. Irregular Polygon If a polygon is not equiangular and equilateral, then it is an irregular polygon

9. Polygons named by number of sides 11 sided polygon - hendecagon

10. Diagonal of a polygon A diagonal of a polygon is a segment that connects 2 nonconsecutive vertices.

11. Convex polygon In a convex polygon, every diagonal lies inside it

12. Concave polygon In a concave polygon, at least 1 diagonal can be drawn so that part of it contains points in the exterior of the polygon

13. Congruent polygons If 2 polygons have the same size and shape, they are congruent

14. Interior and Exterior angles of polygons At each vertex, there are 2 special angles. An interior angle is an angle fprmed by 2 sides of a polygon with a common vertex An exterior angles is an angle formed by 1 side of a polygon and the extension of an adjacent side E I

15. Formula for sum of interior angles of a polygon n is the number of sides sum of interior angles = (n-2) 180 o

16. Formula for interior angles measure of a regular polygon n is the number of sides Each interior angle =

17. Formula for exterior angle measure of a regular polygon n is the number of sides

18. Center of a regular polygon Center is the point that is equidistant from each of the polygon's vertices

19. Central angle of a regular polygon Central angle has its vertex at the center of the polygon and its sides pass through consecutive vertices

20. Formula for central angle measure of a regular polygon n is the number of sides