The Attempt at a Solution
Length of the unstretched springs is L .Suppose block is pushed towards C by a small distance x . This causes a change in length of springs B and C . Their new length is L+∆L .Consider spring B. If the new length makes a small angle θ with the vertical .
I need to find relation between ∆L and x .
Applying cosine rule ,
x2 = (L+∆L)2 + L2 -2L(L+∆L)cosθ
For small angles , cosθ≈1.
Using this I get ∆L = x .
This is not correct . What is the mistake ?