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Question
Find the area of a triangle whose sides are 9 cm, 12 cm and 15 cm ?
Solution
The triangle whose sides are a = 9cm, b = 12 cm and c = 15 cm
The area of a triangle `=sqrt(s(s-a)(s-b)(s-c))`
Here 1s = semi-perimeter of a triangle
`2s = a + b + c`
`s=(a+b+c)/2=(9+12+15)/2=(36)/2=18cm`
∴ area of a triangle= `sqrt(s(s-a)(s-b)(s-c))`
`=sqrt(18(18-9)(18-12)(18-15))=sqrt(18(9)(6)(3))`
`=sqrt(18cm xx3cmxx54cm^2) =54cm^2`
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