Quantitative Aptitude Ques 417

Question: If $ {{(r\cos \theta -\sqrt{3})}^{2}}+r,{{(\sin \theta -1)}^{2}}=0, $ then the value of $ \frac{r\tan \theta +\sec \theta }{r\sec \theta +\tan \theta } $ is equal to

Options:

A) 5/4

B) 4/6

C) $ \sqrt{3}/2 $

D) ½

Show Answer

Answer:

Correct Answer: B

Solution:

  • $ {{(r\cos \theta -\sqrt{3})}^{2}}=0 $

$ \Rightarrow $ $ (r\cos \theta -\sqrt{3})=0 $

$ \Rightarrow $ $ r\cos \theta =\sqrt{3} $ … (i)

$ \Rightarrow $ $ {{(r\sin \theta -1)}^{2}}=0 $

$ \Rightarrow $ $ (r\sin \theta -1)=0 $
$ \Rightarrow $ $ r\sin \theta =1 $ … (ii) On squaring Eqs. (i) and (ii) and adding, $ r^{2}({{\cos }^{2}}\theta +{{\sin }^{2}}\theta )=3+1=4 $
$ \Rightarrow $ $ r=2 $ $ \cos \theta =\frac{\sqrt{3}}{2} $
$ \Rightarrow $ $ \theta =\frac{\pi }{6} $

$ \Rightarrow $ $ \sin \theta =\frac{1}{2} $
$ \Rightarrow $ $ \theta =\frac{\pi }{6} $ $ \frac{r\tan \theta +\sec \theta }{r\sec \theta +\tan \theta }=\frac{2\tan \pi /6+\sec \pi /6}{2\sec \pi /6+\tan \pi /6} $ $ =,\frac{2\times \frac{1}{\sqrt{3}}+\frac{2}{\sqrt{3}}}{2\times \frac{2}{\sqrt{3}}+\frac{1}{\sqrt{3}}}=\frac{\frac{4}{\sqrt{3}}}{\frac{5}{\sqrt{3}}}=\frac{4}{5} $