## Class 9 Maths Chapter 3 Coordinate Geometry

**What is Coordinate geometry?**A coordinate geometry can be defined as a branch of geometry, where the position of the points on the plane is defined with the help of an ordered pair of numbers known as coordinates.

**Applications of Coordinate Geometry**Coordinate Geometry is mainly used for:

Calculating the distance between the two given points.

To describe the equations of different geometric figures.

Finding the equation, midpoint, or slope of a line segment.

For calculating the area and the perimeter of a given polygon.

To conclude the given set of lines are parallel or perpendicular.

**Cartesian system**It consists of two perpendicular lines: one is horizontal and other one is vertical.

The horizontal line is called X-axis and the vertical line is called Y-axis. The point of intersection where these two lines meet is called origin and it is denoted by O.

NOTE: X’OX is called X-axis

YOY’ is called Y-axis.

The two axes (X & Y) divides the Cartesian plane( or XY Plane) into four quadrants I,II,III & IV.

QUADRANT I (+,+) **Example**(3,4)

QUADRANT II- (-,+)**Example**(-6,2)

QUADRANT III- (-,-)**Example**(-3,-5)

QUADRANT IV- (+,-)**Example**(3,-1)

**Coordinates: (x, y)**Here, x coordinate is called

**Abscissa**

y coordinate is called

**Ordinate**

For example: Locate points (5, 0), (0, 5), (5, 2), (-3, 5), (-3, -5) and (5, -3) in the Cartesian plane.

Plot the points (−2,4)(−2,4), (3,3)(3,3), and (0,−3)(0,−3) in the coordinate plane.