RAJASTHAN ­ PET Rajasthan PET Solved Paper-2002

  • question_answer
    \[{{(1+i)}^{6}}+{{(1-i)}^{6}}\]is equal to

    A)  \[16i\]               

    B)  16

    C)  1                 

    D)  0

    Correct Answer: D

    Solution :

     \[{{(1+i)}^{6}}+{{(1-i)}^{6}}\] \[={{(\sqrt{2})}^{6}}{{\left( \frac{1}{\sqrt{2}}+\frac{i}{\sqrt{2}} \right)}^{6}}+{{(\sqrt{2})}^{6}}{{\left( \frac{1}{\sqrt{2}}-\frac{i}{\sqrt{2}} \right)}^{6}}\] \[=8{{\left( \cos \frac{\pi }{4}+i\sin \frac{\pi }{4} \right)}^{6}}+8{{\left( \cos \frac{\pi }{4}-i\sin \frac{\pi }{4} \right)}^{6}}\] \[=8\left( \cos \frac{6\pi }{4}+i\sin \frac{6\pi }{4} \right)+8\left( \cos \frac{6\pi }{4}-i\sin \frac{6\pi }{4} \right)\] \[=8\left[ \cos \frac{3\pi }{2}+i\sin \frac{3\pi }{2}+\cos \frac{3\pi }{2}-i\sin \frac{3\pi }{2} \right]\] \[=8\left[ 2\cos \frac{3\pi }{2} \right]\] \[=8\times 0=0\]


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