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Key Concepts
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1. Types of Quadrilaterals
- Parallelogram: Opposite sides are parallel and equal. Diagonals bisect each other.
- Rectangle: A parallelogram with each angle equal to 90°.
- Rhombus: A parallelogram with all sides equal. Diagonals bisect each other at 90°.
- Square: A rectangle with all sides equal.
- Trapezium: Only one pair of opposite sides is parallel.
2. Properties of Parallelograms
- Opposite angles are equal.
- Consecutive angles are supplementary (sum to 180°).
- A diagonal divides it into two congruent triangles.
3. Mid-point Theorem
The line segment joining the mid-points of two sides of a triangle is parallel to the third side and is half of it.