J & K CET Engineering J and K - CET Engineering Solved Paper-2010

  • question_answer
    If \[A+B+C=\pi ,\]then \[\tan \frac{A}{2}.\tan \frac{B}{2}+\tan \frac{B}{2}.\tan \frac{C}{2}+\tan \frac{C}{2}+\tan \frac{C}{2}.\tan \frac{A}{2}\]is equal to

    A)  \[3\]                

    B)  \[2\]

    C)  \[1\]                 

    D)  \[0\]

    Correct Answer: C

    Solution :

    \[\tan \frac{A}{2}.\tan \frac{B}{2}+\tan \frac{B}{2}.\tan \frac{C}{2}+\tan \frac{C}{2}.\tan \frac{A}{2}\] \[\sqrt{\frac{(s-b)\,(s-c)}{s(s-a)}}\,\,\sqrt{\frac{(s-a)\,(s-c)}{s\,(s-b)}}\] \[+\sqrt{\frac{(s-a)\,(s-c)}{s(s-b)}}\,\,\sqrt{\frac{(s-a)\,(s-b)}{s\,(s-a)}}\] \[=\frac{s-c}{s}+\frac{s-a}{s}+\frac{s-b}{s}\] \[=\frac{3s-(a+b+c)}{s}=\frac{3s-2s}{s}\] \[(\because \,\,2s=a+b+c)\] \[=\frac{s}{s}=1\]


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