Class 9 Maths notes for Coordinate Geometry

What is Co-ordinate geometry?

It a branch of geometry which sets up a definite correspondence between the position of a point in a plane and a pair of algebric numbers called co-ordinates

Important points

1) We require two perpendicular axes to locate a point in the plane. One of them is horizontal and other is Vertical
2) The plane is called Cartesian plane and axis are called the coordinates axis
3) The horizontal axis is called x-axis and Vertical axis is called Y-axis
4) The point of intersection of axis is called origin.
Cartesian plane
5) The distance of a point from y axis is called x - coordinate or abscissa and the distance of the point from x axis is called y - coordinate or Ordinate
6) The x-coordinate and y - coordinate of the point in the plane is written as (x, y) for point and is called the coordinates of the point
7) The Origin has zero distance from both x-axis and y-axis so that its abscissa and ordinate both are zero. So the coordinate of the origin is (0, 0)
8) A point on the x - axis has zero distance from x-axis so coordinate of any point on the x - axis will be (x, 0)
9) A point on the y - axis has zero distance from y-axis so coordinate of any point on the y - axis will be (0, y)
10) The axes divide the Cartesian plane in to four parts. These Four parts are called the quadrants
11) The coordinates of the points in the four quadrants will have sign according to the below table
sign convention in Cartesian plane

How to draw the Graph of a Linear equation

1) Suppose the linear equation is
Prepare a table of values of x and corresponding values of y
So in this particular case

2) Plot these points on the Cartesian plane
3) Join them by the straight line

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