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Complex Numbers Model Question Paper

12th Standard

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Maths

Time : 02:00:00 Hrs
Total Marks : 90
    7 x 1 = 7
  1. If z is a non zero complex number, such that 2iz2 = \(\bar { z } \) then |z| is

    (a)

    \(\cfrac { 1 }{ 2 } \)

    (b)

    1

    (c)

    2

    (d)

    3

  2. The solution of the equation |z| - z = 1 + 2i is

    (a)

    \(\frac { 3 }{ 2 } -2i\)

    (b)

    \(-\frac { 3 }{ 2 } +2i\)

    (c)

    \(2-\frac { 3 }{ 2 } i\)

    (d)

    \(2+\frac { 3 }{ 2 } i\)

  3. If \(\frac { z-1 }{ z+1 } \) is purely imaginary, then |z| is

    (a)

    \(\frac { 1 }{ 2 } \)

    (b)

    1

    (c)

    2

    (d)

    3

  4. If (1+i)(1+2i)(1+3i)...(1+ni) = x + iy, then \(2\cdot 5\cdot 10...\left( 1+{ n }^{ 2 } \right) \) is

    (a)

    1

    (b)

    i

    (c)

    x2+y2

    (d)

    1+n2

  5. If \(\omega =cis\cfrac { 2\pi }{ 3 } \), then the number of distinct roots of \(\left| \begin{matrix} z+1 & \omega & { \omega }^{ 2 } \\ \omega & z+{ \omega }^{ 2 } & 1 \\ { \omega }^{ 2 } & 1 & z+\omega \end{matrix} \right| \)=0

    (a)

    1

    (b)

    2

    (c)

    3

    (d)

    4

  6. If, i2 = -1, then i1 + i2 + i3 + ....+ up to 1000 terms is equal to ________

    (a)

    1

    (b)

    -1

    (c)

    i

    (d)

    0

  7. If a = 3 + i and z = 2 - 3i, then the points on the Argand diagram representing az, 3az and - az are ___________

    (a)

    Vertices of a right angled triangle

    (b)

    Vertices of an equilateral triangle

    (c)

    Vertices of an isosceles

    (d)

    Collinear

  8. 5 x 1 = 5
  9. |z1 + z2|

  10. (1)

    2\(\sqrt { 2 } \)

  11. arg (0)

  12. (2)

    ≤ |z1| + |z2|

  13. arg (-i)

  14. (3)

    n arg (z)

  15. arg (zn)

  16. (4)

    2nㅠ

  17. |2+2i|

  18. (5)

    \(\frac { \pi }{ 2 } \)

    2 x 2 = 4
  19. When z = x + iy, then iz is
    (1) x-iy
    (2) i(x+iy)
    (3) -y+ix
    (4) Rotation of z by 90° in the counter clockwise direction

  20. (1+3i) (1-3i)
    (i) (1)2 - (3i)2
    (2) 1 + 9
    (3) 10
    (4) -8

  21. 6 x 2 = 12
  22. Simplify the following
    i1947+ i1950

  23. Simplify \(\left( \frac { 1+i }{ 1-i } \right) ^{ 3 }-\left( \frac { 1-i }{ 1+i } \right) ^{ 3 }\) into rectangular form

  24. Find z−1, if z = (2 + 3i) (1− i).

  25. Find the following \(\left| \frac { 2+i }{ -1+2i } \right| \) 

  26. Obtain the Cartesian form of the locus of z = x + iy in each of the following cases:
    \(\left[ Re\left( iz \right) \right] ^{ 2 }=3\)

  27. Write in polar form of the following complex numbers
    \(2+i2\sqrt { 3 } \)

  28. 4 x 3 = 12
  29. If \(\frac { z+3 }{ z-5i } =\frac { 1+4i }{ 2 } \), find the complex number z in the rectangular form

  30. Show that the points 1, \(\frac { -1 }{ 2 } +i\frac { \sqrt { 3 } }{ 2 } ,\) and \(\frac { -1 }{ 2 } -i\frac { \sqrt { 3 } }{ 2 } \)  are the vertices of an equilateral triangle.

  31. If |z| = 3, show that \(7\le \left| z+6-8i \right| \le 13\).

  32. If z = x + iy is a complex number such that \(\left| \frac { z-4i }{ z+4i } \right| =1\) show that the locus of z is real axis.

  33. 4 x 5 = 20
  34.  If z = x + iy is a complex number such that Im \(\left( \frac { 2z+1 }{ iz+1 } \right) =0\) show that the locus of z is 2x2+ 2y2+ x - 2y = 0

  35. Solve the equation z3+ 27 = 0

  36. Find all cube roots of \(\sqrt { 3 } +i\)

  37. Simplify: \(\left( -\sqrt { 3 } +3i \right) ^{ 31 }\)

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