Question

find the area of a triangle whose equal sides are 12 cm each and the perimeter is 30 centimetre

Answer 1

so the another side is 6
by using herones formula
√15(3)()3(9)
√3×5×3×3×3×3
so answer is 9√15 ok

Answer 2

let's say we have triangle abc
suppose ab=bc
so,ab=bc=12
perimeter=ab+bc+ac
30=12+12+ac
ac=30-24
ac=6

triangle ABC is right angled triangle
because two sides are same so their opposite angle are also same
a+ b+ c=180
suppose a and c is 45
90+c=180
c =90
so, area of triangle = 1/2×base×altitude
=1/2×12×12

$72cm {}^{2}$