Given that

= (1 – cos θ) (1 + cos θ) (1 + cot² θ)

= (1 – ² θ) (1 + cot² θ)

[∵ (a – b) (a + b) = a² – b²]

= ² θ. ² θ

[∵ 1 – cos² θ = sin² θ; 1 + cot² θ = cosec² θ]

=