Current Affairs 8th Class

Category : 8th Class

 Understanding Quadrilaterals

• Quadrilateral: A closed figure bounded by four line segments is called a quadrilateral. It has four angles and four sides.

• Classification of polygons

• Diagonals: A diagonal is a line segment connecting two non-consecutive vertices of a polygon.

• Convex polygon: A polygon is said to be convex if no portion of its diagonals lies in its exterior. Convex polygons

• Concave polygon: A polygon is said to be concave if some portion of its diagonals lies in its exterior.

• Regular polygon: A polygon that is both equilateral and equiangular is called a regular

e.g., A square (since all its sides are equal and all its angles are equal.)

• The number of sides of a regular polygon whose each exterior angle has a measure \[{{x}^{o}}\] is

\[\frac{{{360}^{o}}}{{{x}^{o}}}\]

• Irregular polygon: A polygon that is either not equilateral or not equiangular or both is called an irregular polygon.

e.g., A rectangle (though it is equiangular, it is not equilateral.)

• Angle sum property: The sum of the measures of the four angles of a quadrilateral is 360°.

• Sum of the interior angles of a regular polygon

Thus, in general, the sum of interior angles of a polygon of 'n' sides is given by

\[\left( n-2 \right)\times {{180}^{o}}\text{ }or\text{ }\left( n-2 \right)\text{ }\times \text{ }2\]right angles or 2n - 4 right angles.

• Sum the exterior angles of a polygon: The sum of the exterior angles of any polygon is

\[{{360}^{o}}\].

Types of quadrilaterals.