Here we have to find the double derivative, so to find double derivative we will just differentiate the first derivative once again with a similar method.
Theorem: y and x are given in a different variable that is θ . We can find dy/dx by finding dy/dθ and dx/dθ and then dividing them to get the required thing.
= - cot (θ/2)
⇒ To find f’’ we will differentiate f’ with θ and then divide with equation (2).