Hg
Name: Class 9 STICK TO YOUR WALL IN STUDY AREA
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The Hg Classes (8
th
to 12
th
) By: Er Hershit Goyal (B.Tech. IIT BHU), 134-SF, Woodstock Floors, Nirvana Country, Sector 50, GURUGRAM +91 9599697178.
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Co-ordinate Geometry
• To locate position of an object on a plane, we need two perpendicular lines.
o Horizontal line - It is called the x – axis.
o Vertical line – It is called the y – axis.
o The plane is called the CARTESIAN PLANE or the COORDINATE PLANE and the lines are called
COORDINATE AXES.
o The point of intersection of the axes is called the ORIGIN.
o The coordinate axes divide the plane into 4 sections known as QUADRANTS.
• Abscissa: The distance of a point from the y-axis is called the x-coordinate or abscissa.
• Ordinate: The distance of a point from the x-axis is called the y-coordinate or ordinate.
• (x, y) are the coordinates of a point where x is abscissa and y is ordinate.
• Any point on the x-axis will be of the form (x, 0) [since, for all such points, the distance from x axis, the
ordinate is 0]
• And Any point on the y-axis will be of the form (0, y) [since, for all such points, the distance from y axis,
the abscissa is 0]
Sign convention:
• All distances to right and above origin are positive (+).
• All distances to the left and bottom of origin are negative (-).
• Origin has coordinates (0,0).
Equations of x & y axis:
• Since on x axis, y-coordinate is zero, therefore its equation is y = 0.
• Since on y axis, x-coordinate is zero, therefore its equation is x = 0.
Equations of a line parallel to x and y axis:
• A line parallel to x axis will be of the form y = k
• A line parallel to y axis will be of the form x = k, where k is its perpendicular distance from origin.
