Engineering
Mathematics
nth Roots of Unity
Question

Let w = 3+i2  and P = {wn : n= 1, 2, 3, …….}. Further H1:{zC:Rez>12} and  H2:{zC:Rez<12}, where C is the set of all complex numbers. If z1 ∈ P ⋂ H1, z2 ∈ ⋂ H2 and O represents the origin, then ∠zO z2 =

 5π6

 π2

 2π3

 π6

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Solution

 

 w=3+i2=cosπ6 + i sinπ6

 P=wn=cos6  +  isin6,n=0,1,2,........,11.

 H1:{zC:  Re(z)>12}

 z1H1

   possible  value  ofz1  are  {(32,  12),  (0,1),  (32,  12)}

 H1={zC:  Re(z)  <  12}

 z2pH2

   possible  values  of  z2  are  {(32,  12),  (1,0),  (32,  12)}

 Now,  possible  angle  z1Oz2  is2π3,5π6,π