JEE Main & Advanced Mathematics Complex Numbers and Quadratic Equations Question Bank Self Evaluation Test - Complex Numbers and Quadratic Equations

  • 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 equal to:

    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 these

    Correct Answer: A

    Solution :

     Given \[\frac{(\cos x+i\sin x)(\cos y+i\sin y)}{(\cot u+i)(1+i\tan \,\,v)}\] \[=\,\,\frac{(cos\,x+i\,sin\,x)(cos\,y+i\,sin\,y)}{(cos\,u+i\,sin\,u)(cos\,\nu +i\,sin\,\nu )}\] \[= sin u cos \nu  [cos \left( x +y - u - v \right)\] \[+\,\,i\,\sin \left( x+y-u-\nu  \right)]\]


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