1. Introduction
This chapter introduces coordinate geometry and the idea of representing points in a plane using coordinates.
- Coordinates help us locate points exactly in a plane.
- The system used is called the Cartesian plane, named after René Descartes.
2. Cartesian Plane
- A Cartesian plane has:
- X-axis: horizontal line
- Y-axis: vertical line
- Origin (O): point where X-axis and Y-axis intersect (0, 0)
- The plane is divided into 4 quadrants:
| Quadrant | X-coordinate | Y-coordinate |
|---|---|---|
| I | + | + |
| II | – | + |
| III | – | – |
| IV | + | – |
Note: Coordinates are written as (x, y).
3. Points and Coordinates
- A point on the plane is represented by a pair of numbers: (x,y)
- x = distance from Y-axis (horizontal movement)
- y = distance from X-axis (vertical movement)
Examples:
- P(3,4): 3 units along X-axis, 4 units along Y-axis
- Q(−2,5): 2 units left of Y-axis, 5 units above X-axis
4. Plotting Points
Steps to plot a point (x, y):
- Start at the origin (0,0)
- Move x units along X-axis: right if positive, left if negative
- Move y units along Y-axis: up if positive, down if negative
- Mark the point
5. Quadrants
- Quadrant I: (+, +) → Right and Up
- Quadrant II: (-, +) → Left and Up
- Quadrant III: (-, -) → Left and Down
- Quadrant IV: (+, -) → Right and Down
Example: (−3,−4) is in Quadrant III.
6. Distance Between Points
- Horizontal distance between (x1,y1) and (x2,y1) = ∣x2−x1∣
- Vertical distance between (x1,y1) and (x1,y2) = ∣y2−y1∣
- Distance formula (optional for reference):
Distance=(x2−x1)2+(y2−y1)2
7. Types of Points
- Origin: (0, 0)
- Points on X-axis: y = 0 (example: (5,0))
- Points on Y-axis: x = 0 (example: (0, -3))
- Points in Quadrants: coordinates according to the quadrant rules
8. Simple Geometrical Figures on the Plane
- Shapes can be plotted using points:
- Triangle: 3 points
- Rectangle / Square: 4 points
- Example: Rectangle with vertices (1,1),(1,4),(5,4),(5,1)
- Plot points and join them to visualize the shape.
9. Reflection and Symmetry
- Reflection about X-axis: Change sign of y → (x,y)→(x,−y)
- Reflection about Y-axis: Change sign of x → (x,y)→(−x,y)
10. Summary Table
| Concept | Key Idea |
|---|---|
| Cartesian Plane | X-axis + Y-axis, origin O(0,0) |
| Coordinates | (x, y) – x: horizontal, y: vertical |
| Quadrants | I(+,+), II(-,+), III(-,-), IV(+,-) |
| Plotting a Point | Start at origin, move x then y, mark |
| Distance (horizontal) | |
| Distance (vertical) | |
| Reflection X-axis | (x, y) → (x, -y) |
| Reflection Y-axis | (x, y) → (-x, y) |
11. Key Tips
- Always label axes clearly.
- Check the sign of coordinates before plotting.
- Use grid lines for accuracy.
- Remember origin is (0,0).
Class 7 Maths – Chapter 3: A Peek Beyond the Point
50 Mixed-Type Questions
Section A: Multiple Choice Questions (MCQs) – 10 Questions
- The point where X-axis and Y-axis intersect is called:
a) Quadrant I
b) Origin
c) Coordinate
d) Axis - Which of the following points lies on the Y-axis?
a) (0, 5)
b) (3, 0)
c) (-2, -3)
d) (4, 2) - Point (–3, 4) lies in:
a) Quadrant I
b) Quadrant II
c) Quadrant III
d) Quadrant IV - If a point has coordinates (x, 0), it lies on:
a) X-axis
b) Y-axis
c) Origin
d) Quadrant I - The coordinates of the origin are:
a) (1, 0)
b) (0, 1)
c) (0, 0)
d) (1, 1) - Which quadrant has coordinates (+, –)?
a) I
b) II
c) III
d) IV - The reflection of (3, –4) about X-axis is:
a) (3, 4)
b) (–3, 4)
c) (–3, –4)
d) (3, –4) - The distance between points (0, 0) and (0, 5) is:
a) 0
b) 5
c) √5
d) 25 - Which of the following points lies in Quadrant III?
a) (–2, –3)
b) (3, 2)
c) (–1, 4)
d) (5, –3) - If a rectangle has vertices at (1,1), (1,4), (5,4), and (5,1), the length along X-axis is:
a) 3
b) 4
c) 5
d) 1
Section B: Fill in the Blanks – 10 Questions
- The plane formed by X-axis and Y-axis is called the _______.
- The first coordinate in (x, y) is called the _______.
- The second coordinate in (x, y) is called the _______.
- Point (0, 0) is called the _______.
- A point (–4, 3) is in Quadrant _______.
- Coordinates of a point on X-axis have _______ as their second number.
- Coordinates of a point on Y-axis have _______ as their first number.
- The reflection of (–2, 5) about Y-axis is _______.
- The reflection of (3, –4) about X-axis is _______.
- The horizontal distance between (2, 5) and (7, 5) is _______.
Section C: Short Answer Questions – 10 Questions
- Plot the points (2, 3), (–2, 3), (–2, –3), and (2, –3) and identify the quadrant of each.
- Find the coordinates of a point 4 units to the right of the origin and 3 units above the X-axis.
- Find the reflection of the point (5, –2) about X-axis.
- Find the reflection of the point (–3, 6) about Y-axis.
- A point lies 6 units left of Y-axis and 2 units above X-axis. Write its coordinates.
- Name the quadrants of points (–4, 2), (3, –5), and (–1, –3).
- Determine the vertical distance between points (5, 2) and (5, 8).
- Determine the horizontal distance between points (–3, 7) and (2, 7).
- What are the coordinates of the midpoint between points (2, 3) and (6, 7)?
- If a point lies on the X-axis, its y-coordinate is _______.
Section D: Long Answer / Problem-Solving – 10 Questions
- Plot a triangle with vertices (1,1), (4,1), and (1,5). Find the lengths of its sides.
- Plot a rectangle with vertices (–1,1), (3,1), (3,4), and (–1,4). Find its area.
- A point P is at (3, 4). A point Q is at (3, –2). Find the vertical distance between P and Q.
- The distance between points A(–2, –3) and B(–2, 2) is _______.
- A square has vertices at (0,0), (0,3), (3,3), (3,0). Find its perimeter.
- Find the coordinates of a point which is 5 units right and 4 units above the origin.
- Plot points (1,2), (2,4), (3,6), (4,8) and check whether they lie on a straight line.
- Find the midpoint of line segment joining (–3, –4) and (5, 2).
- If a point (x, y) is reflected about X-axis, how do the coordinates change? Give one example.
- A triangle has vertices (0,0), (0,3), and (4,0). Find its area.
Section E: Application / Higher-Order Thinking – 10 Questions
- A rectangle has vertices (–2,1), (2,1), (2,4), and (–2,4). Find its area and perimeter.
- A point lies 3 units left of Y-axis and 7 units below X-axis. Write its coordinates and quadrant.
- Reflect point (–4, –3) about Y-axis and X-axis, and write new coordinates.
- Plot points (2,3), (–2,3), (–2,–3), (2,–3) and name the quadrants of each point.
- A line segment has endpoints (–2, 5) and (4, 5). Find its length.
- Find the distance between points (–3, 0) and (3, 0).
- Midpoint of (–4, 6) and (2, –2) is _______.
- Write coordinates of a point on the X-axis 7 units to the right of origin.
- A rectangle’s vertices are (1,1), (1,5), (6,5), (6,1). Find its area.
- Determine the quadrant for points (5,–3), (–7,4), (–2,–6), (8,9).
Answers – Chapter 3: A Peek Beyond the Point
Section A: MCQs – Answers
- b) Origin – Intersection of X-axis and Y-axis.
- a) (0, 5) – On Y-axis, x = 0.
- b) Quadrant II – x negative, y positive.
- a) X-axis – y = 0 for all points on X-axis.
- c) (0, 0) – Origin coordinates.
- d) IV – x positive, y negative.
- a) (3, 4) – Reflection about X-axis: y → -y.
- b) 5 – Vertical distance = |5 – 0| = 5 units.
- a) (–2, –3) – Quadrant III.
- b) 4 – Length along X-axis = 5 – 1 = 4.
Section B: Fill in the Blanks – Answers
- Cartesian plane
- x-coordinate / abscissa
- y-coordinate / ordinate
- Origin
- II – x negative, y positive
- 0 – y = 0 for points on X-axis
- 0 – x = 0 for points on Y-axis
- (2, 5) – Change sign of x (reflection about Y-axis)
- (3, 4) – Change sign of y (reflection about X-axis)
- 5 – Horizontal distance = |7 – 2| = 5
Section C: Short Answer – Answers
- (2,3) → Quadrant I; (–2,3) → Quadrant II; (–2,–3) → Quadrant III; (2,–3) → Quadrant IV
- Coordinates = (4,3)
- Reflection about X-axis: (5, 2) → (5, –2)
- Reflection about Y-axis: (–3, 6) → (3, 6)
- Coordinates = (–6, 2)
- Quadrants: (–4,2) → II; (3,–5) → IV; (–1,–3) → III
- Vertical distance = |8 – 2| = 6
- Horizontal distance = |2 – (–3)| = 5
- Midpoint = ((2+6)/2, (3+7)/2) = (4, 5)
- y = 0
Section D: Long Answer / Problem-Solving – Answers
- Triangle sides:
- Base: 4 – 1 = 3 units
- Height: 5 – 1 = 4 units
- Hypotenuse: √[(4–1)² + (5–1)²] = √[3² + 4²] = 5 units
- Rectangle:
- Length = 3 – (–1) = 4
- Width = 4 – 1 = 3
- Area = 4 × 3 = 12 units²
- Vertical distance = |4 – (–2)| = 6 units
- Distance = |–3 – (–2)| = |–3 + 2| = 5 units? Wait step carefully: A(–2,–3), B(–2,2): vertical distance = |2 – (–3)| = 5 units ✔
- Perimeter = 4 × side = 4 × 3 = 12 units
- Coordinates = (5,4)
- Check line: Slope between consecutive points = (4–3)/(2–1) = 1/1 =1; all slopes =1 → yes, straight line
- Midpoint = ((–3+5)/2, (–4+2)/2) = (1, –1)
- Reflection about X-axis: (x,y) → (x,–y); Example: (2,3) → (2,–3)
- Area of triangle = ½ × base × height = ½ × 4 × 3 = 6 units²
Section E: Application / Higher-Order Thinking – Answers
- Rectangle vertices (–2,1), (2,1), (2,4), (–2,4)
- Length = 2 – (–2) = 4
- Width = 4 – 1 = 3
- Area = 4 × 3 = 12
- Perimeter = 2(4 + 3) = 14 units
- Coordinates = (–3, –7), Quadrant III
- Reflections:
- About Y-axis: (4, –3)
- About X-axis: (–4, 3)
- Quadrants:
- (2,3) → I
- (–2,3) → II
- (–2,–3) → III
- (2,–3) → IV
- Length = |4 – (–2)| = 6 units
- Distance = |3 – (–3)| = 6 units
- Midpoint = ((–4+2)/2, (6 + (–2))/2) = (–1, 2)
- Point on X-axis 7 units right of origin: (7,0)
- Rectangle area = (6–1) × (5–1) = 5 × 4 = 20 units²
- Quadrants:
- (5,–3) → IV
- (–7,4) → II
- (–2,–6) → III
- (8,9) → I