Railways Sample Paper RRBs Assistant Loco Pilot and Technician CBT STAGE-I Sample Paper-13

  • question_answer
    If \[\tan 2\theta \tan \theta =1,\]then the general value of \[\theta \] is

    A)  \[\left( n+\frac{1}{2} \right)\frac{\pi }{3}\]

    B)  \[\left( n\frac{1}{2} \right)\pi \]

    C)  \[\left( 2n\pm \frac{1}{2} \right)\frac{\pi }{3}\]    

    D)         None of these

    Correct Answer: A

    Solution :

    \[\tan 2\theta \tan \theta =1\] \[\Rightarrow \]   \[\text{tan}2\theta =\cot \theta \] \[\Rightarrow \]   \[2\theta =\tan \left( \pi /2-\theta  \right)\] \[\Rightarrow \]   \[2\theta =n\pi +\left( \pi /2-\theta  \right)\] \[\Rightarrow \]   \[3\theta =n\pi +\pi /2\] \[\therefore \]      \[\theta =\left( n+\frac{1}{2} \right)\frac{\pi }{3}\]


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