Prove the following identities: `(1-costheta)/(1+costheta)=(cos e ctheta-cottheta)^2`

Explanation

To prove the identity

\[ \frac{1 - \cos \theta}{1 + \cos \theta} = \left( \cot \theta - \cos \theta \right)^2, \]

we will start by simplifying the left-hand side (LHS) and show that it equals the right-hand side (RHS).

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