Quadrilaterals

• The part of the plane lying outside the boundary is called the exterior of the quadrilateral. Each point of this part is called an exterior point of the quadrilateral.
• The sum of the angles of a quadrilateral is 360°
• The part of the plane lying inside the boundary is called the interior of the quadrilateral. Each point of this part is called an interior point of the quadrilateral.
• QUADRILATERAL REGION: The Interior of the quadrilateral together with its boundary is called the quadrilateral region
• Trapezium: A quadrilateral having one and only one pair of parallel sides is called a trapezium.

  A trapezium is said to be an isosceles trapezium if it's nonparallel sides are equal.

  The diagonals of an isosceles trapezium are always equal
• Rhombus: A parallelogram in which all the sides are equal is called a rhombus.

  Properties of a rhombus:

  i) The opposite sides of a rhombus are parallel

  ii) All the sides of a rhombus are equal.

  iii) The opposite angles of a rhombus are equal.

  iv) The diagonals of a rhombus bisect eachother at right angles.
• Rectangle: A parallelogram in which each angle is a right angle is called a rectangle.

  Properties of a rectangle:

  i) Opposite sides of a rectangle are equal and parallel.

  ii) Each angle of a rectangle is 90°.

  iii) The diagonals of a rectangle are equal.
• Square: A parallelogram in which all the sides are equal and each angle is a right angle is called a square.

  Properties of a square:

  i) The sides of a square are all equal.

  ii) Each angle of a square is 90°.

  iii) The diagonals of a square are equal and bisect eachother at right angles.
• Parallelogram: a quadrilateral in which both pairs of opposites sides are parallel is called a parallelogram.

  Properties of a parallelogram:

  i) Opposite sides of a parallelogram are equal and parallel.

  ii) The opposite angles of a parallelogram are equal.

  iii) The diagonals of a parallelogram bisect eachother.