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).
3 sides = Triangle
4 sides = Quadrilateral
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.
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.