Simplify the following: $\left(1 + \cot^2 \theta\right)\left(1 − \cos \theta\right)\left(1 + \cos \theta\right)$

1 -5 3 -3

1

( 1 + cot²θ ) . ( 1 - cosθ). ( 1 + cos θ ) = ( 1 + cot²θ ) . ( 1 - cos²θ ) { using , sin²θ + cos²θ = 1 } = ( 1 + cot²θ ) . (sin²θ ) = ( sin²θ + cos²θ ) = 1