Question

an isosceles triangle has perimeter 30 cm and each of equal sides is 12 cm. find the area of triangle

Answer 1

perimeter =30÷2=15,s=15
now by herons formula
√s(s-12)(s-12)(s-6)
√15(15-12)(15-12)(15-6)
√15 *3*3*9
√3*5*3*3*3*3
=9√15
=34.8

I hope it will help you !

Answer 2

let Base=b
equal sides = 12 cm
perimeter =30 cm
perimeter =Base+equal sides =b+12+12
30 cm = b+24
b=30 cm -24 cm
b= 6 cm
s = a+b+c/2
s=30/2 =15 cm
(s-a) =(15-6)=9 cm
(s-b) =(15-12)=6 cm
(s-c) =(15-12)=6 cm
area of isosceles triangle =
$\sqrt{s \times s - a \times s - b \times s - c} \: \: sq.unit \\ \sqrt{15 \times 9\times 3 \times 3} cm {?}^{2} \\ \sqrt{15 \times9 \times 9 } cm { }^{2} \\ 9 \sqrt{15} cm {?}^{2}$