Lines and Angles
Short Answer Questions
1. What is a point?
Answer:
A point shows an exact location. It has no length, breadth, or height.
2. What is a line segment?
Answer:
A line segment is the shortest distance between two points and has two endpoints.
3. What is a line?
Answer:
A line is formed when a line segment is extended endlessly in both directions.
4. What is a ray?
Answer:
A ray is a part of a line that starts from one point and extends endlessly in one direction.
5. How many lines can pass through one point?
Answer:
Infinite (many) lines can pass through one point.
6. How many lines can pass through two points?
Answer:
Only one unique line can pass through two points.
7. What is an angle?
Answer:
An angle is formed by two rays having a common starting point.
8. What are the parts of an angle?
Answer:
- Vertex (common point)
- Arms (two rays)
9. What is the measure of:
a) Right angle
b) Straight angle
c) Full turn
Answer:
a) 90°
b) 180°
c) 360°
10. Define acute and obtuse angles.
Answer:
- Acute angle: Less than 90°
- Obtuse angle: More than 90° but less than 180°
Long Answer Questions
1. Explain the difference between a line, line segment, and ray.
Answer:
| Concept | Description |
|---|---|
| Line Segment | Has two endpoints and fixed length |
| Line | Extends endlessly in both directions |
| Ray | Starts from one point and extends endlessly in one direction |
Example:
- AB → Line segment
- Line AB → Infinite both sides
- Ray AB → Starts at A, goes through B
2. Explain how an angle is formed and how it is named.
Answer (Step-by-step):
- Take two rays starting from the same point.
- The common point is called the vertex.
- The rays are called arms.
- Name the angle using three letters:
- Middle letter is always the vertex.
Example:
If rays BD and BE meet at B:
- Angle is written as ∠DBE or ∠EBD
3. How can you compare two angles?
Answer (Step-by-step):
Method 1: Superimposition
- Place one angle over the other.
- Match the vertices.
- Compare the opening of arms.
Result:
- Larger opening → Larger angle
- Same opening → Equal angles
4. Explain types of angles with their measures.
Answer:
| Type of Angle | Measure |
|---|---|
| Acute Angle | Between 0° and 90° |
| Right Angle | 90° |
| Obtuse Angle | Between 90° and 180° |
| Straight Angle | 180° |
| Reflex Angle | Between 180° and 360° |
Example:
- 45° → Acute
- 120° → Obtuse
- 200° → Reflex
5. How do you measure an angle using a protractor?
Answer (Step-by-step):
- Place the center of the protractor on the vertex.
- Align one arm of the angle with the 0° line.
- Look where the second arm crosses the scale.
- Read the number (in degrees).
Example:
If the arm crosses at 30°,
→ Angle = 30°
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