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Complex Numbers 5 Mark Book Back Question Paper With Answer Key

12th Standard

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Maths

Time : 01:00:00 Hrs
Total Marks : 120

    5 Marks

    24 x 5 = 120
  1. Find the values of the real numbers x and y, if the complex numbers (3−i)x−(2−i)y+2i +5 and 2x+(−1+2i)y+3+ 2i are equal.

  2. If z1= 2 + 5i, z= -3 - 4i, and z= 1 + i, find the additive and multiplicate inverse of z1, z2 and z3

  3. Show that \(\left( \frac { 19+9i }{ 5-3i } \right) ^{ 15 }-\left( \frac { 8+i }{ 1+2i } \right) ^{ 15 }\) is purely imaginary.

  4. Show that \(\left( 2+i\sqrt { 3 } \right) ^{ 10 }-\left( 2-i\sqrt { 3 } \right) ^{ 10 }\) is purely imaginary

  5. Let z1, z2 and z3 be complex numbers such that \(\left| { z }_{ 1 } \right\| =\left| { z }_{ 2 } \right| =\left| { z }_{ 3 } \right| =r>0\) and z1+ z2+ z3 \(\neq \) 0 prove that \(\left| \frac { { z }_{ 1 }{ z }_{ 2 }+{ z }_{ 2 }{ z }_{ 3 }+{ z }_{ 3 }{ z }_{ 1 } }{ { z }_{ 1 }+{ z }_{ 2 }+{ z }_{ 3 } } \right| \) = r

  6. If z1, z2, and z3 are three complex numbers such that |z1| = 1, |z2| = 2|z3| = 3 and |z+ z+ z3| = 1, show that |9z1z+ 4z1z+ z2z3| = 6

  7. If the area of the triangle formed by the vertices z, iz and z + iz is 50 square units, find the value of |z|

  8.  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

  9. If \(\frac { 1+z }{ 1-z } =cos2\theta +isin2\theta \), show that z = i tan\(\theta\)

  10. If \(cos\alpha +cos\beta +cos\gamma =sin\alpha +sin\beta +sin\gamma =0\) then show that 
    (i) \(cos3\alpha +cos3\beta +cos3\gamma =3cos(\alpha +\beta +\gamma )\)
    (ii) \(sin3\alpha +sin3\beta +sin3\gamma +sin3\gamma =3sin\left( \alpha +\beta +\gamma \right) \)

  11. If z = x + iy and arg \(\left( \frac { z-i }{ z+2 } \right) =\frac { \pi }{ 4 } \), then show that x+ y+ 3x - 3y + 2 = 0

  12. Find the value of \(\left( \cfrac { 1+sin\frac { \pi }{ 10 } +icos\frac { \pi }{ 10 } }{ 1+sin\frac { \pi }{ 10 } -icos\frac { \pi }{ 10 } } \right) ^{ 10 }\)

  13. If \(\omega \neq 1\) is a cube root of unity, show that the roots of the equation (z −1)3 + 8 = 0 are \(-1,1-2\omega ,1-2{ \omega }^{ 2 }\).

  14. If \(\omega \neq 1\) is a cube root of unity, show that \(\left( 1-\omega +{ \omega }^{ 2 } \right) ^{ 6 }+\left( 1+\omega -{ \omega }^{ 2 } \right) ^{ 6 }=128\)

  15. Find the quotient \(\frac { 2\left( cos\frac { 9\pi }{ 4 } +isin\frac { 9\pi }{ 4 } \right) }{ 4\left( cos\left( \frac { -3\pi }{ 2 } + \right) isin\left( \frac { -3\pi }{ 2 } \right) \right) } \) in rectangular form

  16. Suppose z1, zand zare the vertices of an equilateral triangle inscribed in the circle |z| = 2. If z1 = 1 + i\(\sqrt { 3 } \) then find z2 and z3.

  17. Solve the equation z3+ 8i = 0, where \(z \in \mathbb{C}\)

  18. Find the fourth roots of unity.

  19. Find the cube roots of unity.

  20. Simplify: (1+i)18

  21. Show that \(\left( \frac { 19-7i }{ 9+i } \right) ^{ 12 }+\left( \frac { 20-5i }{ 7-6i } \right) ^{ 12 }\) is real

  22. If \(\omega \neq 1\) is a cube root of unity, show that \(\left( 1+\omega \right) \left( 1+{ \omega }^{ 2 } \right) \left( 1+{ \omega }^{ 4 } \right) \left( 1+{ \omega }^{ 8 } \right) ...\left( 1+{ \omega }^{ { 2 }^{ 11 } } \right) =1\).

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

  24. Show that \(\left( 2+i\sqrt { 3 } \right) ^{ 10 }+\left( 2-i\sqrt { 3 } \right) ^{ 10 }\) is real

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