J & K CET Engineering J and K - CET Engineering Solved Paper-2005

  • question_answer
    If \[y=(1+\tan \,A)\,(1-\tan B),\]where  \[A-B=\frac{\pi }{4},\]then \[{{(y+1)}^{y+1}}\] is equal to      

    A)  \[9\]

    B)  \[4\]

    C)  \[27\]

    D)  \[81\]

    Correct Answer: C

    Solution :

    Given, \[A-B=\frac{\pi }{4}\] \[\Rightarrow \] \[\tan (A-B)=\tan \frac{\pi }{4}\] \[\Rightarrow \] \[\frac{\tan A-tanB}{1+\tan \,A\,\tan {{B}^{-1}}}\] \[\Rightarrow \] \[\tan A-\tan B-\tan A\,\tan B=1\] ??(i) Also given,  \[y=(1+\tan A)(1-\tan B)\] \[=(1-tanB+\tan A-\tan A\,\tan B)\] \[=(1+1)\] [from Eq. (i)] \[=2\] \[\therefore \]    \[{{(y+1)}^{y+1}}={{(2+1)}^{2+1}}={{3}^{3}}=27\]


You need to login to perform this action.
You will be redirected in 3 sec spinner