2. What is a Quadrilateral?
• A quadrilateral is a closed polygon with four
sides, four vertices, and four angles. The sum
of its interior angles is always 360°.
4. Properties of a Parallelogram
• 1. Opposite sides are equal and parallel.
• 2. Opposite angles are equal.
• 3. Diagonals bisect each other.
• 4. Sum of adjacent angles is 180°.
5. Properties of a Rectangle
• 1. Opposite sides are equal and parallel.
• 2. All angles are 90°.
• 3. Diagonals are equal and bisect each other.
6. Properties of a Square
• 1. All sides are equal.
• 2. All angles are 90°.
• 3. Diagonals are equal, bisect each other at
90°, and bisect the angles.
7. Properties of a Rhombus
• 1. All sides are equal.
• 2. Opposite angles are equal.
• 3. Diagonals bisect each other at 90°.
• 4. Diagonals bisect the angles.
8. Properties of a Trapezium
• 1. One pair of opposite sides is parallel.
• 2. Adjacent angles on the same side of a non-
parallel side are supplementary.
9. Midpoint Theorem
• The line joining the midpoints of two sides of a
triangle is parallel to the third side and is half
of its length.
10. Theorem on Diagonals of a
Parallelogram
• In a parallelogram, the diagonals bisect each
other.
11. Example Problem
• In a parallelogram ABCD, diagonal AC = 10 cm
and diagonal BD = 8 cm. Find the length of AO
and BO.
• Solution:
• Since diagonals bisect each other, AO = 5 cm,
BO = 4 cm.
12. Conclusion
• • Quadrilaterals have unique properties based
on their types.
• • Understanding theorems helps solve
complex problems.
• • Practice with real-life examples for better
understanding.
