CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2010

  • question_answer
    If\[{{z}_{1}}=\sqrt{2}\left( \cos \frac{\pi }{4}+i\sin \frac{\pi }{4} \right)\]and\[{{z}_{2}}=\sqrt{3}\left( \cos \frac{\pi }{3}+i\sin \frac{\pi }{3} \right),\]then\[|{{z}_{1}}{{z}_{2}}|\]is

    A)  \[6\]                                    

    B)  \[\sqrt{2}\]

    C)  \[\sqrt{6}\]                       

    D)         \[\sqrt{3}\]

    E)  \[\sqrt{2}+\sqrt{3}\]

    Correct Answer: C

    Solution :

    Given that \[{{z}_{1}}=\sqrt{2}\left( \cos \frac{\pi }{4}+i\sin \frac{\pi }{4} \right)\]                                 \[=1+i\]\[\therefore \]\[|{{z}_{1}}|=\sqrt{{{1}^{2}}+{{1}^{2}}}=\sqrt{2}\] and      \[{{z}_{2}}=\sqrt{3}\left( \cos \frac{\pi }{3}+i\sin \frac{\pi }{3} \right)\]                 \[=\frac{\sqrt{3}}{2}+\frac{3i}{2}\] \[\therefore \]  \[|{{z}_{2}}|=\sqrt{\left( \frac{\sqrt{3}}{2} \right)+{{\left( \frac{3}{2} \right)}^{2}}}\]                 \[=\sqrt{\frac{3}{4}+\frac{9}{4}}=\frac{2\sqrt{3}}{2}=\sqrt{3}\] \[\therefore \]  \[|{{z}_{1}}{{z}_{2}}|=|{{z}_{1}}|.|{{z}_{2}}|\]                                 \[=\sqrt{2}.\sqrt{3}=\sqrt{6}\]


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