JEE Main & Advanced Sample Paper JEE Main Sample Paper-1

  • question_answer
    \[\int_{{}}^{{}}{\sqrt{\frac{\cos x-{{\cos }^{3}}x}{1-{{\cos }^{3}}x}}}dx\] ax is equal to

    A)  \[\frac{2}{3}{{\sin }^{-1}}({{\cos }^{3/2}}x)+c\]

    B)  \[\frac{3}{2}{{\sin }^{-1}}({{\cos }^{3/2}}x)+c\]

    C)  \[\frac{2}{3}{{\cos }^{-1}}({{\cos }^{3/2}}x)+c\]

    D)  None of the above

    Correct Answer: C

    Solution :

    Put\[I=\sqrt{\frac{\cos x(1-{{\cos }^{2}}x)}{1-{{\cos }^{3}}x}}dx\] \[=\int_{{}}^{{}}{\frac{\sqrt{\cos x}\sin x}{\sqrt{1-{{({{\cos }^{3/2}}x)}^{2}}}}}dx\] Put\[{{\cos }^{3/2}}x=t\Rightarrow \frac{3}{2}\sqrt{\cos x}(-\sin x)dx=dt\] \[\therefore \]\[I=\frac{2}{3}\int_{{}}^{{}}{\frac{-dt}{\sqrt{1-{{t}^{2}}}}=\frac{2}{3}{{\cos }^{-1}}(t)+c}\] \[=\frac{2}{3}{{\cos }^{-1}}({{\cos }^{3/2}}x)+c\]


You need to login to perform this action.
You will be redirected in 3 sec spinner