CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2001

  • question_answer
    The value of k for which \[{{(cos\text{ }x+sin\text{ }x)}^{2}}+k\text{ }sin\text{ }x\,cos\text{ }x-1=0\]is an identity, is:

    A)  \[-1\]                                   

    B)  \[-2\]

    C)  0                            

    D)         1

    E)  2

    Correct Answer: B

    Solution :

    \[{{(cos\text{ }x+sin\text{ }x)}^{2}}+k\text{ }sin\text{ }x\text{ }cos\text{ }x-1=0\] \[\Rightarrow \] \[si{{n}^{2}}x+co{{s}^{2}}x+2\text{ }sin\text{ }x\text{ }cos\text{ }x+\] \[k\text{ }sin\text{ }x\text{ }cos\text{ }x-1=0\] \[\Rightarrow \]\[2\text{ }sin\text{ }x\text{ }cos\text{ }x=-k\text{ }sin\text{ }x\text{ }cos\text{ }x\] \[\Rightarrow \]               \[k=-2\]


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