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CBSE Science MCQ 

     Complex Numbers
Submitted by: Suresh Gyanchandani (Jaipur) 

1.   Find real values of x and y for which the complex numbers           –3 +  ix2y and x2 + y + 4i  are conjugate of each other.
 
2.   If a + ib =  c + i  , prove that a2 + b2 = 1 and  b  =    2c   
                       c - i                                              a      c2 –1
 
3.  Express the following complex numbers in the polar form:

     (i) 1 + i           (ii 2 + 6 /3 i

                                   5 + /3 i

 
4.  Find the square root of –7 – 24i.
 
5.  If ( x + iy)1/3 = a + ib, prove that x/a + y/b = 4(a2 – b2)
 
6.  Put the following in the form r(cos q  + i sin q), where r is a positive real number and  180 < q <180:     ( 1 + 7i )

                                                       ( 2 – i ) 2

 
7.  Convert the complex number,            i  –  1     ,  into polar form.

                                                   cos 60 + i sin 60

 
8.  If z = 2 –3i, prove that z2 –4z + 13 = 0.
 
9.  If z1 = 2 + i , z2 = 2 – 3i , z3 = 4 + 5i , evaluate:  Im ( z 2 .  z3   
                                                                                           z1
               
10. If  ( a + i)2  = p + iq , show that p2 + q2 =  ( a2 + 1 )2

          ( 2a – i)                                                  (4a2 + 1 )

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