Find the area of an isosceles triangle whose equal sides are 12 cm each and the perimeter is 30 cm.

Consider △ABC as the isosceles triangle. Here, AB = AC = 12 cm. Perimeter = 30 cm ⇒ AB + AC + BC = 30 ⇒ 12 + 12 + BC = 30 ⇒ BC = 30 - 24 = 6 cm. We know that, Semi-perimeter (s) = = 15 cm. Area of an isosceles triangle = , where a is length of equal sides and b is the length of other side. Substituting values we get, Hence, area of isosceles triangle = 34.86 cm 2 .