First Understand Polygons. Polygons are many-sided figures, with sides that are line segments. Polygons are named according to the number of sides and angles they have. The most familiar polygons are the triangle, the rectangle, and the square. A regular polygon is one that has equal sides.

**A triangle is the simplest polygon, having three sides and three angles. The sum of the three angles of a triangle is equal to 180 degrees.**