JEE Main & Advanced Mathematics Differential Equations Question Bank Miscellaneous differential equations

  • question_answer
    The solution of the differential equation \[{{\cos }^{2}}x\frac{{{d}^{2}}y}{d{{x}^{2}}}=1\] is

    A)            \[y=\log \cos x+cx\]                

    B)            \[y=\log \sec x+{{c}_{1}}x+{{c}_{2}}\]

    C)            \[y=\log \sec x-{{c}_{1}}x+{{c}_{2}}\]                                

    D)            None of these

    Correct Answer: B

    Solution :

                        \[{{\cos }^{2}}x\frac{{{d}^{2}}y}{d{{x}^{2}}}=1\] Þ \[\frac{{{d}^{2}}y}{d{{x}^{2}}}={{\sec }^{2}}x\]            On integrating, we get \[\frac{dy}{dx}=\tan x\pm {{c}_{1}}\]            Again integrating, we get \[y=\log \sec x\pm {{c}_{1}}x\pm {{c}_{2}}\].


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