Question

find the area of a triangle two side of which are 18 cm and 10 cm and the perimeter is 42 CM​

Answer 1

Step-by-step explanation:

10+18+18=46 cm

that is perimeter

form a triangle using given sides

then,

use formula area that is 1/2b×h

or √s[(s-a)(s-b)(s-c)]

then you will get the answer

Answer 2

To Find

The area of triangle

Given

The perimeter is 42 cm

One side of triangle is 18 cm

Second side of triangle is 10 cm

Suppose the third side of triangle is 'x'

Now Three sides of triangles are

18 cm 10 cm and x cm.

$\implies\sf \: Now \: \: perimeter = 18+10+x \\ \implies \tt \: 42cm = 18 + 10 + x \\ \implies \tt \:42cm = 28 + x \\ \tt \:x = 42 - 28cm \\ \tt \:x = = 21cm$

Semi perimeter of triangle

42/2 = 21cm

Using Heron's Formula..

$\boxed {\underline{\sqrt{s(s - a)(s - b)(s - c)} }}$

The area of triangle is :

$\sf {{\sqrt{s(s - a)(s - b)(s - c)} }} \\ \\ \sf \: \sqrt{21(21 - 18)(21 - 10)(21 - 14} \: {cm}^{2} \\ \\ \sf \: \sqrt{21 \times 3 \times 11 \times 7} \: {cm}^{2} \\ \\ 21\sqrt{11} \: \sf {cm}^{2}$

$\red{\sf \: Hence \: the \: area \: of \: triangle \: is \: 21 \sqrt{11 \: {cm}^{2} } }$

Hope it helps you amii