Answer:
Option A. 5²(2-√3)
Step-by-step explanation:
In an isosceles triangle b = c = 5 and ∠A = π/6
By cosine rule in any triangle
a² = b² + c² - 2bc cosA
By putting the values of b, c and ∠A in the equation
a² = 5² + 5² - 2×5×5×cos(π/6) = 25 + 25 - (50√3/2) = 50 - 25√3
a² = 25(2-√3) = 5²(2-√3)
Therefore the answer is Option A. 5²(2 - √3)
