A) $ \frac{3}{5} $
B) $ \frac{1}{5} $
C) $ \frac{2}{5} $
D) $ \frac{4}{5} $
Correct Answer: A
$ \therefore $ $ BC=1 $ and $ AB=2 $ Now, $ {{(AC)}^{2}}={{(AB)}^{2}}+{{(BC)}^{2}} $
$ \Rightarrow $ $ {{(AC)}^{2}}={{(2)}^{2}}+{{(1)}^{2}} $
$ \Rightarrow $ $ AC=\sqrt{5} $
$ \therefore $ $ cosec\theta =\frac{AC}{BC}=\sqrt{5} $ and $ \sec \theta =\frac{AC}{AB}=\frac{\sqrt{5}}{2} $
$ \therefore $ $ \frac{cose{c^{2}}\theta -{{\sec }^{2}}\theta }{cose{c^{2}}\theta +{{\sec }^{2}}\theta }=\frac{{{(\sqrt{5})}^{2}}-{{( \frac{\sqrt{5}}{2} )}^{2}}}{{{(\sqrt{5})}^{2}}+{{( \frac{\sqrt{5}}{2} )}^{2}}} $ $ =\frac{5-\frac{5}{4}}{5+\frac{5}{4}}=\frac{15}{25}=\frac{3}{5} $