RAJASTHAN ­ PET Rajasthan PET Solved Paper-2001

  • question_answer
     \[\int_{0}^{\pi /2}{\frac{\sqrt[3]{{{\sin }^{2}}x}dx}{\sqrt[3]{{{\sin }^{2}}x}\sqrt[3]{{{\cos }^{2}}x}}}\]is equal to

    A)  \[\frac{\pi }{4}\]

    B)  \[\frac{\pi }{2}\]

    C)  \[\pi \]

    D)  \[2\pi \]

    Correct Answer: A

    Solution :

     Let \[I=\int_{0}^{\pi /2}{\frac{\sqrt[3]{{{\sin }^{2}}x}}{\sqrt[3]{{{\sin }^{2}}x}+\sqrt[3]{{{\cos }^{2}}x}}}dx\]  ...(i) \[\Rightarrow \]\[I=\int_{0}^{\pi /2}{\frac{\sqrt[3]{{{\sin }^{2}}(\pi /2-x)}}{\sqrt[3]{{{\sin }^{2}}(\pi /2-x)}+\sqrt[3]{{{\cos }^{2}}(\pi /2-x)}}}dx\] \[=\int_{0}^{\pi /2}{\frac{\sqrt[3]{{{\cos }^{2}}x}}{\sqrt[3]{{{\cos }^{2}}x}+\sqrt[3]{{{\sin }^{2}}x}}}dx\] ?.(ii) On adding Eqs. (i) and (ii), \[2I=\int_{00}^{\pi /2}{1dx}\] \[\Rightarrow \] \[2I=[x]_{0}^{\pi /2}=\frac{\pi }{2}\] \[\Rightarrow \] \[I=\frac{\pi }{4}\]


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