Simplify $\sqrt{\dfrac{1 - \text{sin}^2 \text{ θ}}{1 - \text{cos}^2 \text{ θ}}}$.

Substituting, 1 - sin² θ = cos² θ and 1 - cos² θ = sin² θ in $\sqrt{\dfrac{1 - \text{sin}^2 \text{ θ}}{1 - \text{cos}^2 \text{ θ}}}$ we get :

$\Rightarrow \sqrt{\dfrac{\text{cos}^2 \text{ θ}}{\text{sin}^2 \text{ θ}}} \\[1em] \Rightarrow \sqrt{\text{cot}^2 \text{ θ}} \\[1em] \Rightarrow \text{cot θ}.$

Hence, $\sqrt{\dfrac{1 - \text{sin}^2 \text{ θ}}{1 - \text{cos}^2 \text{ θ}}}$ = cot θ.