- A1
- B3
- C4
- D2
Step-by-Step Solution
A quadrilateral has 4 vertices. Number of diagonals = n(n-3)/2 = 4(1)/2 = 2. They join the two pairs of non-adjacent vertices.
Answer: D) 2
How many diagonals does a quadrilateral have?
Class 9QuadrilateralsGeometry — Quadrilaterals
Key idea: Special parallelograms
**Rectangle** (parallelogram + all angles 90°):
- All properties of a parallelogram.
- Diagonals are EQUAL (in addition to bisecting each other).
**Rhombus** (parallelogram + all sides equal):
- All properties of a parallelogram.
- Diagonals bisect each other AT RIGHT ANGLES.
- Diagonals also bisect the angles of the rhombus.
**Square** (rectangle + rhombus):
- All properties of both.
- Diagonals: equal, bisect at right angles, AND bisect angles.
- All properties of a parallelogram.
- Diagonals are EQUAL (in addition to bisecting each other).
**Rhombus** (parallelogram + all sides equal):
- All properties of a parallelogram.
- Diagonals bisect each other AT RIGHT ANGLES.
- Diagonals also bisect the angles of the rhombus.
**Square** (rectangle + rhombus):
- All properties of both.
- Diagonals: equal, bisect at right angles, AND bisect angles.
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