An isosceles triangle has perimeter 30cm and each of the equal sides is 12cm. Find the area of the triangle.
Solution:
Let the third side of the triangle be x⇒Perimeter=30 cm semiperimeter(s)=perimeter/2⇒2S=30,S=15 Given:⇒12+12+x=30⇒x=6⇒A=√s(s−a)(s−b)(s−c) (Heron's formula)⇒A=√15(15-12)(15-12)(15-6)=√15(3)(3)(9)⇒A=9√15 cm2