The polygon is the flat geometrical figure consisting of the pieces which are crossed in three or more points. At the same time the polygon is the closed broken line.
In a polygon of a point are tops, and pieces – the parties. The tops belonging to the same party of a polygon are called adjacent. The piece which connects any two tops which are not lying on one party is called diagonal. The polygon with n-tops is called the n-square and the number of the parties has n-oye. It divides the plane into two parts: internal and external areas. The polygon which points lie on one side from each straight line is passed through two of its next tops, is called convex. A corner of a convex polygon at this top is called the corner formed by two of its parties for which this top is the general. An external corner of a convex polygon at this top is called the corner adjacent to an internal corner of a polygon at this top.
The circle is called entered in a polygon if all parties of a polygon concern it, and the polygon then is described about this circle. The circle is called described about a polygon if all tops of a polygon lie on a circle, therefore, the polygon is called inscribed in a circle.
Triangles, quadrangles, pentagons are examples of polygons. A triangle is called the geometrical figure consisting of three points which are not lying on one straight line and three pieces which are in pairs connecting these points. The polygon having four parties (and four corners), is called a quadrangle. Examples of polygons are trapezes and parallelograms. A trapeze is called the quadrangle at which two parties are parallel (bases), and two other (side) do not. A parallelogram is called the quadrangle at which the opposite sides are in pairs parallel. A rectangle – a parallelogram which has all right angles. A rhombus – a parallelogram at which all parties are equal. The square is a rectangle which also has all equal parties. Such polygon at which all parties and corners are equal is called regular. Any regular polygon is convex.