Question

find the area of a triangle two sides which are 18cm and 10cm and the perimeter is 42cm
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Answer 1

AnswEr :-

Let ,

first side = a = 10.

second side = b = 18cm

third side = c

Given that perimeter = 42cm.

so, perimeter = a+b+c = 42 cm.

=>  c = 42-28

=> c =14cm.

By herons formula,

 Area = √s(s-a)(s-b)(s-c)

Here , s = a+b+c/ 2 =  42/2  = 21.

Therefore , Area = √21(21-18)(21-10)(21-14)

                           = √ 21×21×11

                       = 21√11 cm².

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