SSC Quantitative Aptitude Trigonometry Question Bank Trigonometry (II)

  • question_answer
    If \[\tan (x+y)tan(x-y)=1,\]then the value of \[\tan \left( \frac{2x}{3} \right)\]is

    A) \[\frac{1}{\sqrt{3}}\]

    B) \[\frac{2}{\sqrt{3}}\]

    C) \[\sqrt{3}\]

    D) \[1\]

    Correct Answer: A

    Solution :

    [a] Given,\[\tan (x+y)\tan (x-y)=1\] \[\Rightarrow \]   \[\tan \,(x+y)=\cot (x-y)\] \[\Rightarrow \]   \[\tan \,(x+y)=\tan \,[90{}^\circ -(x-y)]\] \[\Rightarrow \]   \[=h\,m\] \[\Rightarrow \]   \[2x=90{}^\circ \] \[\therefore \]      \[x=\frac{90{}^\circ }{2}=45{}^\circ \] \[\therefore \]      \[\tan \left( \frac{2x}{3} \right)=\tan \left( \frac{2\times 45{}^\circ }{3} \right)\] \[=\tan 30{}^\circ =\frac{1}{\sqrt{3}}\]


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