A presentation on Coordinate geometry for Classes VIII and IX

2. Co-ordinate Geometry : The branch of mathematics in which
geometric problems are solved through algebra by using the
coordinate system is known as coordinate geometry.

3. Why do we need
Coordinate geometry:
To locate an object
or a point in a plane.
Here the plane is
called Cartesian or
coordinate plane
which is combination
of two coordinate
axis. The horizontal
line is called abscissa
and vertical line is
called ordinate.

4. The horizontal line is
called the X-axis and
vertical line is called
Y-axis.
The point of
intersection is called
origin.
The coordinates of the
origin are (0,0)
The distance of a point
from the Y-axis is
called abscissa.
The distance of a point
from X-axis is called
ordinate.
The plane is called the
Cartesian, and the lines
are called coordinate
axes.
Here
OB is called abscissa and AB is
called Ordinates.

5. Quadrants:
XX’ O
Y
Y’
III
III IV
(+,+)(-,+)
(-,-) (+,-)

6. Coordinates
XX’
Y
Y’
O
Origin
1 2 3 4
+ve direction
-1-2-3-4
-ve direction
-1
-2
-3
-vedirection
1
2
3
+vedirection
X-axis : XOX’
Y-axis : YOY’

7. What is coordinate of a point:
Coordinate of a point means an ordered pair
of numbers that give the location of a point on a
graph. Let us understand the position of a point
from the graph.
1
2
3
4
5
0
6
1 2 3 4 50 6
(3,4)

8. The first number in an ordered pair is always the
x or abscissa and the second number is always
the y or the ordinate..
1
3
2
4
5
0
6
1 2 3 4 50 6
(3,4)

9. How to find coordinate of a point
Step 1-Always find the x value first, moving horizontally either
right (positive) or left (negative).
Step 2 – Starting from your new position find the y value by
moving vertically either up (positive) or down (negative
1
3
2
4
5
0
6
1 2 3 4 50 6
(2,3)y
x

10. Now let us find the co-ordinate of the point as
shown in the graph
1
3
2
4
5
0
6
1 2 3 4 50 6
(5,4)
y
x

11. Quadrants
XX’ O
Y
Y’
III
III IV
(+,+)(-,+)
(-,-) (+,-)
Q : (1,0) lies in which Quadrant?
Ist? IInd?
A : None. Points which lie on the axes do not lie in any
quadrant.

12. Example: Finding coordinate of a point .
XX’
Y
Y’
O
1 2 3 4-1-2-3-4
-1
-2
-3
1
2
3
(2,1)
(-3,-2)
Abcissa
(?,?)