BCECE Engineering BCECE Engineering Solved Paper-2005

  • question_answer
    The value of \[\int_{0}^{\pi /2}{\frac{\frac{\pi }{4}-x}{\sqrt{\sin x+\cos x}}dx}\]is:

    A) \[\frac{\pi \sqrt{3}}{4}\]     

    B)         \[\frac{\pi }{4\sqrt{2}}\]    

    C)         0                            

    D)         none of these

    Correct Answer: C

    Solution :

    Let \[I=\int_{0}^{\pi /2}{\frac{\frac{\pi }{4}-x}{\sqrt{\sin x}+\cos x}}dx\]                                ?(i) \[\Rightarrow \]\[I=\int_{0}^{\pi /2}{\frac{\frac{\pi }{4}-\left( \frac{\pi }{2}-x \right)}{\sqrt{\sin \left( \frac{\pi }{2}-x \right)+\cos \left( \frac{\pi }{2}-x \right)}}dx}\] \[\Rightarrow \]               \[I=\int_{0}^{\pi /2}{\frac{x-\frac{\pi }{4}}{\sqrt{\cos x+\sin x}}}dx\]                       ?(ii) On adding Eqs. (i) and (ii), we get \[2I=\int_{0}^{\pi /2}{\frac{0}{\sqrt{\sin x+\cos x}}dx}\] \[\Rightarrow \]               \[I=0\]


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