Class 9 Math Chapter 3 Coordinate Geometry

Class 9 Math Chapter 3 Coordinate Geometry

Basic Concepts

Question: How can a dot’s position on paper be precisely described?
Answer: By specifying distances from two edges (e.g., 5 cm from the left edge and 9 cm from the bottom).

Question: What is the key idea behind locating any point?
Answer: Two independent measurements (e.g., column and row).

Question: What classroom activity demonstrates position description?
Answer: The “Seating Plan” activity (using rows and columns to label desks).

Cartesian System

Question: What are the two perpendicular lines in the Cartesian system?
Answer: The x-axis (horizontal) and y-axis (vertical).

Question: What is the origin?
Answer: The intersection point (0, 0) of the x-axis and y-axis.

Question: What direction is OX on the x-axis?
Answer: The positive direction.

Question: How many quadrants are in the coordinate plane?
Answer: Four (I, II, III, IV).

Question: What is another name for the coordinate plane?
Answer: Cartesian plane or xy-plane.


Coordinates & Conventions

Question: What is the x-coordinate called?
Answer: Abscissa.

Question: What is the y-coordinate called?
Answer: Ordinate.

Question: How are coordinates written?
Answer: As (x, y) in brackets, with the abscissa first.

Question: What are the coordinates of the origin?
Answer: (0, 0).

Question: What are the coordinates of any point on the x-axis?
Answer: (x, 0).

Question: What are the coordinates of any point on the y-axis?
Answer: (0, y).


Quadrants & Signs

Question: What is the sign of coordinates in Quadrant I?
Answer: (+, +).

Question: What is the sign of coordinates in Quadrant II?
Answer: (−, +).

Question: What is the sign of coordinates in Quadrant III?
Answer: (−, −).

Question: What is the sign of coordinates in Quadrant IV?
Answer: (+, −).

Question: Can (x, y) ever equal (y, x)?
Answer: Only if x = y.


Key Figures & Facts

Question: Who developed coordinate geometry?
Answer: René Descartes.

Question: What is the global convention for writing coordinates?
Answer: Abscissa (x) first, ordinate (y) second.

Question: What is the y-coordinate of any point on the x-axis?
Answer: 0.

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