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 Trapezium with parallel sides a and b, and the distance between
two parallel sides as ‘h’.

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

(a)Area  (a b h
)
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(b)Perimeter= Sum of two parallel sides + Sum of two non-parallel sides
 Regular hexagon with side ‘a’
Area = 6  Area of an equilateral triangle with side „a‟

2
2
 6 3 a  3 3a .
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Area of Triangle-by using Heron’s Formula

We have known that the area of special triangles could be obtained using the triangle
formula.

Generally, the area of triangle is given by the following formula:
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Area of a triangle = x base x height sq. unit
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However, for a triangle with the sides being given usually, calculation of height would
not be simple. For the same reason, we rely on Heron‟s Formula to calculate the area of
the triangles with the given lengths.Heron‟s formula is given as,

Area of a Triangle (A)= s s − a s − b s − c ,

Where, „a‟, „b‟ and „c‟ are the sides of the triangle and „S‟ is the semi -perimeter of the
triangle.

+ +
S=
2

Generally, this formula is used when the height of the triangle is not possible to find or
you can say if the triangle is scalene triangle.

Example-1

Find the area of triangular park whose three sides are 40 m, 24 m and 32 m
respectively.

Solution:
Here, a = 40 m, b = 24 m and c = 32 m
Therefore, s = + + = 40+24+32 = 48 m.
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