- A81
- B90
- C180
- D99
Step-by-Step Solution
Adjacent angles sum to 180°. Their halves sum to 90°. In the triangle formed, the third angle (between the bisectors) = 180 − 90 = 90°.
Answer: B) 90
In a parallelogram, the bisectors of two adjacent angles meet at a point. The angle between these bisectors is ____ degrees.
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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