Quantitative Aptitude Ques 284

Question: If $ 7{{\sin }^{2}}\theta +3{{\cos }^{2}}\theta =4, $ then the value of $ tan\theta $ is ( $ \theta $ is acute)

Options:

A) $ \frac{1}{\sqrt{2}} $

B) $ \sqrt{3} $

C) $ \frac{1}{\sqrt{3}} $

D) 1

Show Answer

Answer:

Correct Answer: C

Solution:

  • $ 7{{\sin }^{2}}\theta +3{{\cos }^{2}}\theta =4 $

$ \Rightarrow $ $ 7{{\sin }^{2}}\theta +3-3{{\sin }^{2}}\theta =4 $
$ \Rightarrow $ $ 4{{\sin }^{2}}\theta +3=4 $

$ \Rightarrow $ $ {{\sin }^{2}}\theta =\frac{1}{4} $
$ \Rightarrow $ $ \sin \theta =\frac{1}{2}=\sin 30{}^\circ $

$ \Rightarrow $ $ \theta =30{}^\circ $

$ \therefore $ $ tan\theta =tan30{}^\circ =\frac{1}{\sqrt{3}} $