Co-ordinate geometry

Class 9 - NCERT

Intro:

• Ex:
  1. Street numbers, house number
  2. position of dot in a white paper
  3. Seating plan
• position of any object lying in a plane can be represented with the help of 2 perpendicular lines
• This is Co-ordinate geometry
• developed by French Philosopher and Mathematician Rene Descartes

Ex. 3.1

1. find the co-ordinates
2. mark in graph

Cartesian system:

• the point in positive direction at a distance 'r' from the origin represents the number 'r' and same for '-r'
• horizontal line XX' - number line
• vertical line YY' - lift
• Origin (0,0)
• four parts - Quadrants
  1. • +
• the plane is known as Cartesian plane, Co-ordinate plane, XY plane
• the axes is known as Co-ordinate axes
• x co-ordinate = abscissa - perpendicular distance from y-axis measured along x-axis
• y co-ordinate = ordinate - perpendicular distance from x-axis measured along y-axis
• place the co-ordinates always in ( brackets )
• y co-ordinate is always zero for point lying on x-axis
• x co-ordinate is always zero for point lying on y-axis
• if x=y, then (x,y) = (y,x) not other wise

Ex. 3.2

1. mark the points on graph
2. find the co-ordinates