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Complex Numbers 3 Mark Book Back Question Paper With Answer Key

12th Standard

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Maths

Time : 00:30:00 Hrs
Total Marks : 156

    3 Marks

    52 x 3 = 156
  1. Find the value of the real numbers x and y, if the complex number (2+i)x+(1−i)y+2i −3 and x+(−1+2i)y+1+i are equal

  2. If z= 1 - 3i, z= - 4i, and z3 = 5 , show that (z+ z2) + z= z1+ (z+ z3)

  3. If z= 3, z= -7i, and z= 5 + 4i, show that z1(z+ z3) = zz+ zz3

  4. Write \(\frac { 3+4i }{ 5-12i } \) in the x + iy form, hence find its real and imaginary parts.

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

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

  7. If z1= 3 - 2i and z= 6 + 4i, find \(\frac { { z }_{ 1 } }{ z_{ 2 } } \) in the rectangular form.

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

  9. The complex numbers u, v, and w are related by \(\frac { 1 }{ u } =\frac { 1 }{ v } +\frac { 1 }{ w } \) If v = 3−4i and w = 4+3i, find u in rectangular form.

  10. If z= 3 + 4i, z= 5 -12i, and z3 = 6 + 8i, find |z1|, |z2|, |z3|, |z1+z2|, |z2-z3| and |z1+z3|

  11. If |z| = 2 show that \(3\le \left| z+3+4i \right| \le 7\)

  12. 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.

  13. For any two complex number z1 and z2 such that |z1| = |z2| = 1 and z1z2 \(\neq \) -1, then show that \(\frac { { z }_{ 1 }+{ z }_{ 2 } }{ 1+{ z }_{ 1 }{ z }_{ 2 } } \) is real number.

  14. Which one of the points 10 − 8i, 11+ 6i is closest to 1 + i.

  15. If |z| = 1, show that \(2\le \left| { z }^{ 2 }-3 \right| \le 4\)

  16. If \(\left| z-\frac { 2 }{ z } \right| =2\) show that the greatest and least value of |z| are \(\sqrt { 3 } +1\) and \(\sqrt { 3 } -1\) respectively.

  17. Show that the equation \({ z }^{ 3 }+2\bar { z } =0\) has five solutions

  18. Show that the following equations represent a circle, and find its centre and radius \(\left| z-2-i \right| =3\)

  19. Obtain the Cartesian equation for the locus of z = x + iy in each of the following cases:
    |z - 4| = 16

  20. Find the rectangular form of the complex numbers
    \(\left( cos\frac { \pi }{ 6 } +isin\frac { \pi }{ 6 } \right) \left( cos\frac { \pi }{ 12 } +isin\frac { \pi }{ 12 } \right) \)

  21. If (x+ iy1)(x+ iy2)(x3 + iy3)...(xn+ iyn) = a + ib, show that
    (x1+ y12)(x2+ y22)(x3+ y32)...(xn+ yn2) = a+ b2

  22. If \(\omega \neq 1\) is a cube root of unity, then the show that \(\cfrac { a+b\omega +c{ \omega }^{ 2 } }{ b+c\omega +{ a\omega }^{ 2 } } +\cfrac { a+b\omega +{ c\omega }^{ 2 } }{ c+a\omega +b{ \omega }^{ 2 } } =-1\)

  23. Show that \(\left( \frac { \sqrt { 3 } }{ 2 } +\frac { i }{ 2 } \right) ^{ 5 }+\left( \frac { \sqrt { 3 } }{ 2 } -\frac { i }{ 2 } \right) ^{ 5 }=-\sqrt { 3 } \)

  24. If \(2cos\alpha=x+\frac { 1 }{ x } \) and \(2cos\ \beta =y+\frac { 1 }{ y } \), show that \({ x }^{ m }{ y }^{ n }+\frac { 1 }{ { x }^{ m }{ y }^{ n } } =2cos(m\alpha +n\beta )\)

  25. Solve the equation z3+ 27 = 0

  26. Find the value of \(\sum _{ k=1 }^{ 8 }{ \left( cos\frac { 2k\pi }{ 9 } +isin\frac { 2k\pi }{ 9 } \right) } \).

  27. If z = 2−2i, find the rotation of z by θ radians in the counter clockwise direction about the origin when \(\theta =\frac { \pi }{ 3 } \).

  28. Show that |3z−5+i| = 4 represents a circle, and, find its centre and radius.

  29. Show that |z+2−i|<2 represents interior points of a circle. Find its centre and radius.

  30. Represent the complex number −1−i

  31. Find the principal argument Arg z, when z = \(\frac { -2 }{ 1+i\sqrt { 3 } } \)

  32. Find the product \(\frac { 3 }{ 2 } \left( cos\frac { \pi }{ 3 } +isin\frac { \pi }{ 3 } \right) .6\left( cos\frac { 5\pi }{ 6 } +isin\frac { 5\pi }{ 6 } \right) \)in rectangular from

  33. If z = x + iy and arg\(\left( \frac { z-1 }{ z+1 } \right) =\frac { \pi }{ 2 } \), then show that x+ y= 1.

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

  35. Simplify \(\left( \frac { 1+cos2\theta +isin2\theta }{ 1+cos2\theta -isin2\theta } \right) ^{ 30 }\)

  36. If \(z=\left( cos\ \theta +isin\ \theta \right) \), show that \({ z }^{ n }+\frac { 1 }{ { z }^{ n } } =2cos\ n\theta \) and \({ z }^{ n }-\frac { 1 }{ { z }^{ n } } =2i\ sin\ n\theta \)

  37. Simplify \(\left( sin\frac { \pi }{ 6 } +icos\frac { \pi }{ 6 } \right) ^{ 18}\)

  38. Given the complex number z = 2 + 3i, represent the complex numbers in Argand diagram z, −iz , and z−iz

  39. If z= 1-3i, z= - 4i, and z3 = 5, show that (z1z2)z= z1(z2z3)

  40. If z= 3, z= -7i, and z= 5 + 4i, show that (z+ z2)z= z1z+ z+ z3

  41. Show that the following equations represent a circle, and, find its centre and radius
    \(\left| 2z+2-4i \right| =2\)

  42. Show that the following equations represent a circle, and, find its centre and radius
    |3z-6+12i| = 8

  43. Obtain the Cartesian equation for the locus of z = x + iy in each of the following cases:
    |z - 4|2- |z -1 |= 16

  44. Find the rectangular form of the complex numbers
    \(\frac { cos\frac { \pi }{ 6 } -isin\frac { \pi }{ 6 } }{ 2\left( cos\frac { \pi }{ 3 } +isin\frac { \pi }{ 3 } \right) } \)

  45. If z = 2−2i, find the rotation of z by θ radians in the counter clockwise direction about the origin when \(\theta =\frac { 2\pi }{ 3 } \).

  46. If z = 2−2i, find the rotation of z by θ radians in the counter clockwise direction about the origin when \(\theta =\frac { 3\pi }{ 2 } \).

  47. Represent the complex numbe \(1+i\sqrt { 3 } \) in polar form.

  48. If | z | = 2 show that \(8 \leq|z+6+8 i| \leq 12\)

  49. If (x+ iy1)(x+ iy2)(x3 + iy3)...(xn+ iyn) = a + ib, show that 
    \(\sum _{ r=1 }^{ n }{ tan^{ -1 } } \left( \frac { { y }_{ r } }{ { x }_{ r } } \right) ={ tan }^{ -1 }\left( \frac { b }{ a } \right) +2k\pi ,k\epsilon Z\)

  50. If \(2\ cos\ \alpha=x+\frac { 1 }{ x } \) and \(2\ cos\ \beta =y+\frac { 1 }{ y } \), show that \(\frac { x }{ y } +\frac { y }{ x } =2cos\left( \alpha -\beta \right) \)

  51. If \(2cos\ \alpha=x+\frac { 1 }{ x } \) and \(2cos\ \beta =y+\frac { 1 }{ y } \), show that ​\(xy-\frac { 1 }{ xy } =2isin\left( \alpha +\beta \right) \)

  52. If \(2cos\ \alpha=x+\frac { 1 }{ x } \) and \(2cos\ \beta =y+\frac { 1 }{ y } \), show that ​\(\frac { { x }^{ m } }{ { y }^{ n } } -\frac { { y }^{ n } }{ { x }^{ m } } =2isin\left( m\alpha -n\beta \right) \)

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