Understanding Quadrilaterals Class 8 PPT

 Page 1


CURVES
? A plane curve is a curve that lies in a single plane or a plane 
surface like paper. A plane curve may be closed or open.
Page 2


CURVES
? A plane curve is a curve that lies in a single plane or a plane 
surface like paper. A plane curve may be closed or open.
POLYGONS
Polygon is a closed
plane figure bounded by
three or more straight sides
that meet in pairs in the same
number of vertices, and do
not intersect other than at
these vertices.
Page 3


CURVES
? A plane curve is a curve that lies in a single plane or a plane 
surface like paper. A plane curve may be closed or open.
POLYGONS
Polygon is a closed
plane figure bounded by
three or more straight sides
that meet in pairs in the same
number of vertices, and do
not intersect other than at
these vertices.
PARTS OF A POLYGON
- The endpoints of the sides of polygons are called vertices. When naming a 
polygon, its vertices are named in consecutive order either clockwise or 
counterclockwise. 
- Consecutive sides are two sides that have an endpoint in common. The four-sided 
polygon in Figure below could have been named ABCD, BCDA, or ADCB, for 
example. It does not matter with which letter you begin as long as the vertices are 
named consecutively. Sides AB and BC are examples of consecutive sides. 
There are four pairs of consecutive sides in this polygon.
Page 4


CURVES
? A plane curve is a curve that lies in a single plane or a plane 
surface like paper. A plane curve may be closed or open.
POLYGONS
Polygon is a closed
plane figure bounded by
three or more straight sides
that meet in pairs in the same
number of vertices, and do
not intersect other than at
these vertices.
PARTS OF A POLYGON
- The endpoints of the sides of polygons are called vertices. When naming a 
polygon, its vertices are named in consecutive order either clockwise or 
counterclockwise. 
- Consecutive sides are two sides that have an endpoint in common. The four-sided 
polygon in Figure below could have been named ABCD, BCDA, or ADCB, for 
example. It does not matter with which letter you begin as long as the vertices are 
named consecutively. Sides AB and BC are examples of consecutive sides. 
There are four pairs of consecutive sides in this polygon.
PARTS OF A POLYGON
A diagonal of a polygon is any segment that joins two nonconsecutive vertices. 
Figure shows five-sided polygon QRSTU. Segments QS , SU , UR , RT and QT are 
the diagonals in this polygon. 
Diagonals of a polygon can be  found with the formula given below :
Page 5


CURVES
? A plane curve is a curve that lies in a single plane or a plane 
surface like paper. A plane curve may be closed or open.
POLYGONS
Polygon is a closed
plane figure bounded by
three or more straight sides
that meet in pairs in the same
number of vertices, and do
not intersect other than at
these vertices.
PARTS OF A POLYGON
- The endpoints of the sides of polygons are called vertices. When naming a 
polygon, its vertices are named in consecutive order either clockwise or 
counterclockwise. 
- Consecutive sides are two sides that have an endpoint in common. The four-sided 
polygon in Figure below could have been named ABCD, BCDA, or ADCB, for 
example. It does not matter with which letter you begin as long as the vertices are 
named consecutively. Sides AB and BC are examples of consecutive sides. 
There are four pairs of consecutive sides in this polygon.
PARTS OF A POLYGON
A diagonal of a polygon is any segment that joins two nonconsecutive vertices. 
Figure shows five-sided polygon QRSTU. Segments QS , SU , UR , RT and QT are 
the diagonals in this polygon. 
Diagonals of a polygon can be  found with the formula given below :
CLASSIFICATION OF POLYGONS
Polygons first fit into two general 
categories— convex and not convex
(sometimes called concave). 
A polygon is concave if there are two 
points somewhere inside it for which a 
segment with these as its endpoints 
cuts at least 2 of the sides of the 
polygon.
A polygon that is not concave is called 
convex