J & K CET Engineering J and K - CET Engineering Solved Paper-2007

  • question_answer
    If \[\alpha +\beta =\frac{\pi }{4},\]then the value of \[(1+\tan \alpha )\] \[(1+\tan \beta )\]is equal to                      

    A)  \[1\]             

    B)  \[-1\]

    C)  \[2\]             

    D)  \[-2\]                

    Correct Answer: C

    Solution :

    Given,   \[\alpha +\beta =\frac{\pi }{4}\] \[\therefore \]  \[\tan (\alpha +\beta )=\tan \left( \frac{\pi }{4} \right)=1\] \[\Rightarrow \]   \[\tan \alpha +\tan \beta =1-\tan \alpha \,\,tan\,\beta \] \[\Rightarrow \]\[\tan \,\,\alpha +\tan \,\,\beta +\tan \,\alpha \,\tan \,\beta =1\] ?.(i) Now,   \[(1+\tan \alpha )\,(1+\tan \beta )\] \[=1+\tan \alpha +\tan \beta +\tan \alpha \,\tan \beta \] \[=1+1=2\] [using Eq. (i)]


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