Parallel and Intersecting Lines
Class 7 Mathematics · Ganita Prakash Part 1 · Chapter 5
CBSE Class 7 community
View all
2- Mathematics
7- Mathematics
- Science
- + 3 more
- Space weighted by chapter size
- Charts from the book's own data
- Traps corrected
- Space weighted by chapter size
- Charts from the book's own data
- Traps corrected
- Social Science
- Space weighted by chapter size
- Charts from the book's own data
- Traps corrected
- Space weighted by chapter size
- Charts from the book's own data
- Traps corrected
- Space weighted by chapter size
- Charts from the book's own data
- Traps corrected
- Space weighted by chapter size
- Charts from the book's own data
- Traps corrected
- Space weighted by chapter size
- Charts from the book's own data
- Traps corrected
Summary
This chapter studies the relationships between lines on a plane. When two lines cross they intersect at a point and form four angles: adjacent angles form a linear pair that adds to \(180^\circ\), and opposite angles are vertically opposite and are always equal. If all four angles are equal, each is \(90^\circ\) and the lines are perpendicular. Lines on the same plane that never meet, however far extended, are parallel. The key tool is the transversal — a line crossing two others, forming eight angles. When a transversal cuts a pair of parallel lines, corresponding angles are equal, alternate angles are equal, and co-interior (same-side interior) angles add to \(180^\circ\). Conversely, equality of corresponding angles is exactly what guarantees that two lines are parallel. You learn to spot, mark and reason about these angle relationships, to draw parallel lines using a ruler and set square or by paper folding, and to prove results rather than rely only on measurement.