Class 9 · Chapter 12
Quadrilaterals
Four-sided figures — angle sum, and the family tree from parallelogram down to square.
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Ganita Manjari · Class 9 (2026-27)
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Detailed theory
Split any quadrilateral along one diagonal into two triangles. Each triangle has angle sum , so the quadrilateral has .
Key concepts & formulas
01
Angle sum of a quadrilateral: .
02
**Parallelogram**: both pairs of opposite sides parallel. Opposite sides and angles equal; diagonals bisect each other.
03
**Rhombus**: parallelogram with all sides equal; diagonals are perpendicular bisectors.
04
**Rectangle**: parallelogram with a right angle (hence all four); diagonals equal.
05
**Square**: both rhombus and rectangle.
06
**Trapezium**: exactly one pair of parallel sides. **Kite**: two pairs of adjacent equal sides.