# Polygons

Polygon, a closed, flat shape, with three or more straight sides and angles.

Angle is the space between two adjacent sides of the polygon. Angles are measured in degrees.

Vertex is the common endpoint of two adjacent sides of the polygon.

Equilateral:  Having all sides or faces equal

Equiangular: Having equal angles.

Regular Polygon is a polygon that is equilateral (all sides of equal length) and equiangular (all angles of equal measure).

Polygon names:

3 sides = Triangle

5 sides = Pentagon

6 sides = Hexagon

8 sides = Octagon

9 sides = Nonagon

10 sides = Decagon

Types of polygons:

Vertex (plural vertices): the point where two sides meet.

Interior Angle: is an angle inside the polygon, formed by two adjacent sides.

A diagonal is a line segment that links two non-adjacent vertices of a polygon.

Triangle Classification (regarding their sides):

Equilateral: Having all sides equal.

Isosceles: Having two equal sides.

Scalene:  Having all sides of different lengths.

Triangle Classification (regarding their angles):

Acute: (all angles are acute [angle<90°])

Right: (one angle is right [angle=90°])

Obtuse: (one angle is obtuse [angle>90°])

Equiangular: (all angles are equal)

Area and  Perimeter.

Perimeter. It is the distance around a figure. Add all sides.  Keywords: fencing, framing, edge, border.

To find the perimeter, just add up the length of all the sides.

Perimeter=A+B+C+D+E+F
Area.  It is the surface space inside a figure.
Keywords:   Cover, Painting, putting grass, putting tiles, Square units.