JEE Main & Advanced Mathematics Differential Equations Question Bank Exact defferential equations

  • question_answer
    Solution of \[(xy\cos xy+\sin xy)dx+{{x}^{2}}\cos xy\,dy=0\] is

    A)                 \[x\sin (xy)=k\]     

    B)                 \[xy\sin (xy)=k\]

    C)                 \[\frac{x}{y}\sin (xy)=k\]    

    D)                 \[x\sin (xy)=k\]

    Correct Answer: A

    Solution :

                       \[[xy\,\cos (xy)+\sin (xy)]dx+{{x}^{2}}\cos (xy)dy=0\]                    \[xy\,\cos (xy)dx+{{x}^{2}}\cos (xy)dy+\sin (xy)dx=0\]                    \[x\,\cos (xy)(ydx+xdy)+\sin (xy)dx=0\]                    \[\cot (xy)dxy+\frac{dx}{x}=0\]                                 \[\log \,\sin (xy)+\log x=k\] Þ \[x\,\sin (xy)=k\].               


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