---
source: ncert
topic: geometry
class_level: class_7
chapter: ch5
difficulty: beginner
---

Class 7 | Ch5: Lines and Angles
Complementary=90° total. Supplementary=180° total. Linear pair=180°. Vertically opposite=EQUAL.
Parallel lines + transversal: 8 angles formed.
Corresponding angles: same position=EQUAL (F-shape).
Alternate interior angles: between lines, alternate sides=EQUAL (Z-shape).
Co-interior angles: between lines, same side=SUPPLEMENTARY=180° (C-shape).
Alternate exterior angles: outside, alternate sides=EQUAL.
Converse: if corresponding/alternate angles equal → lines parallel.
Example: angle=65°. Corresponding=65°. Alternate interior=65°. Co-interior=115°.
Two supplementary angles, one=3 times other: x+3x=180 → x=45°, angles=45° and 135°.
Co-interior angles SUPPLEMENTARY not equal. Vertically opposite ALWAYS equal.