If cot θ=7/8, then find the value of ((1+ sin θ)(1- sin θ))/((1+ cos θ)(1- cos θ)).

\[\begin{aligned} \frac{(1+\sin \theta)(1-\sin \theta)}{(1+\cos \theta)(1-\cos \theta)} & =\frac{1-\sin ^{2} \theta}{1-\cos ^{2} \theta} \\ & =\frac{\cos ^{2} \theta}{\sin ^{2} \theta}=\cot ^{2} \theta \\ & =\left(\frac{7}{8}\right)^{2}=\frac{49}{64} \end{aligned} \]