CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2006

  • question_answer
    The modulus and amplitude of \[{{(1+i\sqrt{3})}^{8}}\] are respectively:

    A)  256 and \[\frac{\pi }{3}\]             

    B)  256 and \[\frac{2\pi }{3}\]

    C)  2and \[\frac{2\pi }{3}\]                

    D)  256 and \[\frac{8\pi }{3}\]

    Correct Answer: B

    Solution :

    Let  \[z={{(1+i\sqrt{3})}^{8}}\] \[={{(-2)}^{6}}{{\left( \frac{1+i\sqrt{3}}{-2} \right)}^{8}}={{(-2)}^{8}}{{({{\omega }^{2}})}^{8}}\] \[={{2}^{8}}\,\,{{\omega }^{16}}={{2}^{8}}\omega \]                       (\[\because \] \[{{\omega }^{3}}=1\]) \[={{2}^{8}}\left( \frac{-1+i\sqrt{3}}{2} \right)\] \[={{2}^{8}}\left( \cos \frac{2\pi }{3}+i\,\,\sin \frac{2\pi }{3} \right)\] \[\therefore \] Modulus \[={{2}^{8}}=256\]and Amplitude \[=\frac{2\pi }{3}\].


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