Two Dimensional Figures

A 2-dimensional figure is a shape with length and width. It can be open or closed

Open figures have ends that do not meet; closed figures begin and end at the same point

Polygons are closed 2-dimensional figures that have 3 or more straight sides. The sides do not cross

Each endpoint where two sides meet is called a vertex (plural: vertices)

A polygon is a flat, 2-dimensional figure made up of 3 or more line segments called sides

Polygons are named after the number of sides. The prefix for a name tells the number of sides

A polygon whose all sides have the same length and whose all angles are of the same size, is a regular polygon

A regular triangle is called an equilateral triangle. It has 3 sides. The 3 angles measure 60° each

A regular quadrilateral is called a square. The 4 angles measure 90° each