Manipal Engineering Manipal Engineering Solved Paper-2012

  • question_answer
    \[A+iB\]form of\[\frac{(\cos x+i\sin x)(\cos y+i\sin y)}{(\cot u+i)(1+i\tan v)}\]is

    A) \[\sin u\cos v[\cos (x+y-u-v)\]\[+i\sin (x+y-u-v)]\]

    B) \[\sin u\cos v[\cos (x+y+u+v)\]\[+i\sin (x+y+u+v)]\]

    C) \[\sin u\cos v[\cos (x+y+u+v)\]\[-i\sin (x+y+u+v)\]

    D)  None of the above

    Correct Answer: A

    Solution :

    \[LHS\] \[=\frac{(\cos x+i\sin x)(\cos y+i\sin y)}{(\cos u+i\sin u)(\cos v+i\sin v)}\sin u\cos v\]                 \[=\sin u\cos v\,\,{{e}^{ix}}\cdot {{e}^{iy}}\cdot {{e}^{-iu}}\cdot {{e}^{-iv}}\]                 \[=\sin u\cos v[\cos (x+y-u-v)\]\[+i\sin (x+y-u-v)]\]


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