Manipal Engineering Manipal Engineering Solved Paper-2008

  • question_answer
    The order of the differential equation whose general solution is given by\[y=({{c}_{1}}+{{c}_{2}})\cos (x+{{c}_{3}})-{{c}_{4}}{{e}^{x\_{{c}_{5}}}}\],    where\[{{c}_{1}},\,\,{{c}_{2}},\,\,{{c}_{3}},\,\,{{c}_{4}},\,\,{{c}_{5}}\]are arbitrary constants, is

    A)  4                                            

    B)  3

    C)  2                            

    D)         5

    Correct Answer: B

    Solution :

    Given,                 \[y=({{c}_{1}}+{{c}_{2}})\cos (x+{{c}_{3}})-{{c}_{4}}{{e}^{x+{{c}_{5}}}}\] \[\Rightarrow \]               \[y=({{c}_{1}}\cos {{c}_{3}}+{{c}_{2}}\cos {{c}_{3}})\cos x\]                 \[=({{c}_{1}}\sin {{c}_{3}}+{{c}_{2}}\sin {{c}_{3}})\sin x-{{c}_{4}}{{e}^{{{c}_{5}}}}{{e}^{x}}\] \[\Rightarrow \]               \[y=A\cos x-B\sin x\cdot C{{e}^{x}}\] where, \[A={{c}_{1}}\cos {{c}_{3}}+{{c}_{2}}\cos {{c}_{3}}\]                 \[B={{c}_{1}}\sin {{c}_{3}}+{{c}_{2}}\sin {{c}_{3}}\] and        \[C=-{{c}_{4}}{{e}^{{{c}_{5}}}}\] Which is an equation containing three arbitrary constant. Hence, the order of the differential equation is 3.


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