(b) \(\frac34\)
\(\sqrt{\frac{(1-sin\,x)(1+sin\,x)}{(1+cos\,x)(1-cos\,x)}}\) = \(\sqrt{\frac{1-sin^2\,x}{1-cos^2\,x}}\) (∵ (a – b) (a+b) = a2 – b2)
= \(\sqrt{\frac{cos^2\,x}{sin^2\,x}}\) (∵ sin2x + cos2x = 1)
= \(\frac{cos\,x}{sin\,x}\) = cot θ = \(\frac{1}{tan\,\theta} = \frac{1}{\frac{4}{3}}=\frac34.\)