Question

6. An isosceles triangle has perimeter 30 cm and each of the equal sides is 12 cm. Find
the area of the triangle.​

Answer 1

Step-by-step explanation:

Perimeter = 30

Each equal sides = 12

Third side = 24 +x =30

x = 30-24 =6

Area = s = 12+12 +6/2 = 30/2 =15

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

$\sqrt{15 \times 3 \times 3 \times 9 \}$

$3 \sqrt{9 \times 15}$

$9 \sqrt{15}$

Answer 2

First,let the third side be x.

It is given that the length of the equal sides us 12 cm and it's perimeter is 30 cm.

So,$30=12+12+x$

$⇒ 30 = 24 + x$

$⇒24 + x = 30$

$⇒ x= 30 - 24$

$⇒ x = 6$

So,the length of the third side is 6 cm.

Thus,the semi perimeter of the isosceles triangle (s) = 30/2 cm =15 cm

By using Heron's Formula,

Area of the triangle,

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

$= \sqrt{15(15 - 12)(15 - 12)(15 - 6)} \: {cm}^{2}$

$= \sqrt{15 \times 3 \times 3 \times 9} \: {cm}^{2}$

$= 9 \sqrt{15} \: {cm}^{2}$