Class 7 Mathematics
Chapter 5: Lines and Angles
STAGE 0: Foundation
Geometry helps us understand shapes, lines, and angles around us. Lines and angles are the basic building blocks of geometry.
Examples in daily life:
- Edges of a book – lines
- Corner of a table – angle
- Crossing roads – intersecting lines
STAGE 1: Lines and Line Segments
- Line: Extends endlessly in both directions
- Line Segment: Has two fixed endpoints
- Ray: Has one endpoint and extends in one direction
STAGE 2: Angles
An angle is formed when two rays meet at a point.
- Vertex: Common endpoint
- Arms: The two rays
Types of Angles:
- Acute Angle – less than 90°
- Right Angle – exactly 90°
- Obtuse Angle – more than 90° but less than 180°
- Straight Angle – 180°
STAGE 3: Adjacent and Vertically Opposite Angles
Adjacent Angles:
- Share a common vertex
- Have a common arm
- Do not overlap
Vertically Opposite Angles:
- Formed when two lines intersect
- Always equal in measure
STAGE 4: Linear Pair
A linear pair of angles is formed when:
- Two adjacent angles lie on a straight line
- Their sum is 180°
Example:
If one angle is 110°, the other angle is 70°.
STAGE 5: Parallel Lines and Transversal
When a line cuts two parallel lines, it forms different angles.
- Corresponding Angles: Equal
- Alternate Interior Angles: Equal
- Co-interior Angles: Sum is 180°
STAGE 6: Practice Questions
1. Define a line segment.
2. What is a right angle?
3. Are vertically opposite angles equal?
4. Find the other angle if one angle of a linear pair is 65°.
5. Name two angles formed when a transversal cuts parallel lines.
Shaktimatha CBSE Learning
Class 7 Mathematics – Chapter 5: Lines and Angles
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