JCECE Engineering JCECE Engineering Solved Paper-2012

  • question_answer
    Find the value of\[{{e}^{iA}}.{{e}^{iB}}.{{e}^{iC}}.{{e}^{iD}}\], where \[A,\,\,\,B,\,\,\,C\] and \[D\] are the angles of a quadrilateral.

    A) \[i\]                                       

    B) \[-i\]

    C) \[1\]                                     

    D) \[-1\]

    Correct Answer: C

    Solution :

    We know that,                 \[{{e}^{i\theta }}=\cos \theta +i\sin \theta \] \[\therefore \]  \[{{e}^{iA}}\cdot {{e}^{iB}}\cdot {{e}^{iC}}\cdot {{e}^{iD}}=(\cos A+i\sin A)\]`\[(\cos B+i\sin B)\cdot (\cos C+i\sin C)\cdot \]\[(\cos D+i\sin D)\] \[=\cos (A+B+C+D)+i\sin (A+B+C+D)\] \[=\cos {{360}^{o}}+i\sin {{360}^{o}}\] \[=1\]


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