Question

the area of an isosceles tangle whose perimeter is 30cm and each of the equal sides is 12cm is

Answer 1

Semiperimeter (s) = 30/2 = 15 
three sides are respectively: 12cm, 12cm and 30-24=6cm

area = sqrt[s(s-a)(s-b)(s-c)]
        = sqrt[ 15(15-12)(15-12)(15-6)]
        = sqrt[ 15*3*3*9]
        = 9 sqrt(15) cm^2

Answer 2

Perimeter=30cm
Third side is 30-24=6
Area=√[s(s-a)(s-b)(s-c)]
a=12,b=12,c=6
S=(12+12+6)/2=15
Area=√{15*3*3*9]=√1215=34.8