BCECE Engineering BCECE Engineering Solved Paper-2009

  • question_answer
    If \[\tan {{1}^{o}}\tan {{2}^{o}}...tan{{2}^{o}}....\tan {{89}^{o}}={{x}^{2}}-8,\]then the value of \[x\]can be

    A) \[\pm \,1\]                        

    B)         \[\pm \,\,2\]                    

    C)         \[\pm \,\,3\]                    

    D)         \[\pm \,\,4\]

    Correct Answer: C

    Solution :

    Given, \[\tan \,{{1}^{o}}\tan {{2}^{o}}...\tan {{89}^{o}}={{x}^{2}}-8\] \[\Rightarrow \]\[\tan {{1}^{o}}\tan {{2}^{o}}...\tan {{44}^{o}}\tan {{45}^{o}}\cot {{44}^{o}}\] \[\Rightarrow \]\[...\,\cot {{2}^{o}}\cot {{1}^{o}}={{x}^{2}}-8\] \[\Rightarrow \]\[1={{x}^{2}}-8\Rightarrow {{x}^{2}}=9\] \[\Rightarrow \]\[x=\pm 3\]


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