CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2001

  • question_answer
    The modulus and amplitude of \[\frac{1+i}{1-i}\] are:

    A)  \[1\]and \[\frac{\pi }{4}\]                           

    B)  \[\sqrt{2}\]and\[\frac{\pi }{3}\]

    C)  1 and \[\frac{\pi }{2}\]                 

    D)  \[-1\]and \[-\pi /2\]

    Correct Answer: C

    Solution :

    \[z=\frac{1+i}{1-i}\times \frac{1+i}{1+i}=\frac{{{(1+i)}^{2}}}{1-{{i}^{2}}}=\frac{1+{{i}^{2}}+2i}{2}=i\] \[i=r(\cos \theta +i\sin \theta )\]                 \[\Rightarrow \]               \[r\cos \theta =0,\,1=r\sin \theta \]                                 \[{{r}^{2}}{{\cos }^{2}}\theta =0,{{r}^{2}}{{\sin }^{2}}\theta =1\]                 \[\Rightarrow \]  \[{{r}^{2}}=1\]                \[\Rightarrow r=1\]                 \[\tan \theta =\frac{1}{0}=\infty \Rightarrow \theta =\pi /2\]


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