Question

The area of an isosceles triangle having base 2 cm and the length of one of the equal sides 4 cm, is 

A. √15 cm²  

B. √15/2 cm² 

C. 2√15 cm² 

D. 4√15 cm²

Answer 1

a = 2, b = 4, c = 4

s = (a + b + c)/2

⇒ s = (2 + 4 + 4)/2 = 10/2 = 5.

Area(Δ) = √s(s-a)(s-b)(s-c)

⇒ Area(Δ) = √5(5-2)(5-4)(5-4)

⇒ Area(Δ) = √5×3×1×1

⇒ Area(Δ) = √15 cm²

Hence, the correct option is A.