CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2005

  • question_answer
    The general solution of \[\sin x-\cos x=\sqrt{2}\] for any integer n is :

    A)  \[n\pi \]                             

    B)  \[2n\pi +\frac{3\pi }{4}\]

    C)  \[2n\pi \]                                           

    D)  \[(2n\pi +1)\]

    Correct Answer: B

    Solution :

    Given that, \[\sin x-\cos x=\sqrt{2}\] \[\Rightarrow \]               \[\frac{1}{\sqrt{2}}\sin x-\frac{1}{\sqrt{2}}\cos x=1\] \[\Rightarrow \,\,\sin {{45}^{o}}\sin x-\cos {{45}^{o}}\cos x=1\] \[\Rightarrow \]                               \[\cos \left( x+\frac{\pi }{4} \right)=-1\] \[\Rightarrow \]                               \[\cos \left( x+\frac{\pi }{4} \right)=\cos \,(\pi )\] \[\Rightarrow \]               \[x+\frac{\pi }{4}=2n\pi +\pi \] \[\Rightarrow \]               \[x=2n\pi +\frac{3\pi }{4}\]


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