CBSE Class 9 Coordinate Geometry | Revision Notes

Key Concepts

• ➥ Coordinate System: A system to locate points on a plane using a pair of numbers.
• ➥ Axes: Two perpendicular lines, the x-axis (horizontal) and the y-axis (vertical).
• ➥ Origin: The point where the axes intersect (0, 0).

Coordinates

➥ An ordered pair (x, y) representing the position of a point.

• ➥ x-coordinate (abscissa): Distance from the y-axis.
• ➥ y-coordinate (ordinate): Distance from the x-axis.

Quadrants

• First Quadrant: (+, +)
• Second Quadrant: (-, +)
• Third Quadrant: (-, -)
• Fourth Quadrant: (+, -)

Plotting Points

➥ Marking a point on the plane using its coordinates (x, y).

Distance Formula

Distance = √((x₂ - x₁)² + (y₂ - y₁)²)

Section Formula

➥ To find a point dividing a line segment between (x₁, y₁) and (x₂, y₂) in the ratio m:n:

((mx₂ + nx₁) / (m+n), (my₂ + ny₁) / (m+n))

Midpoint Formula

➥ To find the midpoint of a line segment between (x₁, y₁) and (x₂, y₂):

((x₁ + x₂) / 2, (y₁ + y₂) / 2)

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Practice Problems

• Plot the points (2, 3), (-1, 4), (-2, -3), (3, -1).
• Find the distance between (1, 2) and (4, 6).
• Determine the midpoint of the line segment joining (3, 5) and (-1, -3).