CBSE Class 8 Maths Notes for Chapter 3 Understanding Quadrilaterals

​POLYGONS
A simple closed curve made up of line segments only is called a polygon.

DIAGONAL
A diagonal is a line segment connecting two non-consecutive vertices of a polygon.
 
CONVEX POLYGONS
Polygons which have no portion of their diagonals in their exteriors are called convex polygons.
 
CONCAVE POLYGONS
Polygons which have some portion of their diagonals in their exteriors are called concave polygons.
 
QUADRILATERALS
1. Parallelogram

• Each pair of opposite sides parallel.
• Opposite sides are equal.
• Opposite angles are equal.
• Diagonals bisect each other.

2. Rhombus

• A parallelogram with sides of equal length.
• Opposite sides are equal.
• Opposite angles are equal.
• Diagonals bisect each other.
• Diagonals are perpendicular to each other.

3. Rectangle

• A parallelogram with a right angle.
• Opposite sides are equal.
• Opposite angles are equal.
• Diagonals bisect each other.
• Each of the angles is a right angle.
• Diagonals are equal.

4. Square

• A rectangle with all equal sides. Opposite sides are equal.
• Opposite angles are equal.
• Diagonals bisect each other.
• Diagonals are perpendicular to each other.
• Each of the angles is a right angle.
• Diagonals are equal.

5. Kite

• A quadrilateral with exactly two pair of equal consecutive sides.
• The diagonals are perpendicular to one another.
• One of the diagonals bisects the other.
• The angle between the unequal sides is equal to each other.