Question

find the area of a triangle two sides of which are 18 centimetre and 10 centimetre and the perimeter is 42 CM

Answer 1

Hope it helps you.
Thank you.

Answer 2

Hey,

Given,
Two sides = 18 cm and 10 cm
let third side be x

We know,
Perimeter = sum of all sides
42 = 18+10 + x
42 - 28 = x
x = 14 cm

We know,
s = a+b+c/2
   = 18+10+14/2
   = 21

We know,
Area = √s(s-a)(s-b)(s-c)
         = √21(21-18)(21-10)(21-14)
         = √ 21* 3 * 11 * 7
        = √21*21*11
        = 21√11 cm²