Difference between polygon curves and non-polygon curves is explained with the help of a diagram.
Polygons are classified according to the number of sides (or vertices). Classification is explained with the help of suitable figures in the table listed in section 3.2.1. Students must understand this concept and remember the classifications given.
A diagonal is a line segment connecting two non-consecutive vertices of a polygon.
After that Convex and concave polygon are discussed. Before moving to angle sum property students will learn about regular and irregular polygons.
A regular polygon is both equiangular and equilateral.
A rectangle is equiangular but not equilateral.
A square has sides of equal length and angles of equal measure that's why it is considered as a regular polygon.
Talking about angle sum property; Angle sum property states that the sum of measures of the three angles of a triangle is 180°.
After going through the introductory section students about the above discussed topics need to solve the problems of exercise 3.1.
Sum of the measure of the exterior angles of a polygon is another topic that will be discussed in this chapter.
The sum of the measures of the external angles of any polygon is 360°.
Various kinds of quadrilaterals are explained like trapezium, parallelogram, etc. Point to be noted that kite is also a special type of quadrilateral. Angles of parallelogram and some special parallelograms are also discussed.
The opposite angles of a parallelogram are of equal measure.
A short note about diagonal of parallelogram is given that in general, diagonals of a parallelogram are not of equal length.
Some special parallelograms are listed in this section like rhombus, square and rectangle.
Properties of all quadrilateral are an important part of this chapter. Students must learn all the properties listed.