Herons Formula - Revision Notes

 CBSE Class 09 Mathematics

Revison Notes

1. Area of a Triangle – by Heron’s Formula

2. Application of Heron’s Formula in finding Areas of Quadrilaterals

  • Triangle with base 'b' and altitude 'h' is

Area =12×(b×h)

  • Area of an isosceles triangle whose equal side is a = a22 square units
  • Triangle with sides a, b and c

(i) Semi perimeter of triangle s =a+b+c2

(ii) Area=s(sa)(sb)(sc)sq. unit

  • Equilateral triangle with side 'a'

Perimeter = 3a units

Altitude = 32a units

Area =34a2 square units

  • Rectangle with length l, breadth b 

Perimeter = 2(l+b)

Area = l×b

  • Square with side a

Perimeter = 4a units

Area = a2  sq. units

Area = (Diagonal)2 sq. units

  • Parallelogra with length l, breadth b and height h

Perimeter = 2(l+b)

Area = b×h

  • Trapezium with parallel sides 'a' & 'b' and the distance between two parallel sides as 'h'.

Area =12(a+b)hsquare units