Unit 1: Number and Algebra

Topic 1.14: De Moivre & roots (HL only) Questions

Practice 20 exam-style questions for IB Math AA SL Topic 1.14. Review the question stems below, then unlock the full Question Bank to access markschemes, model answers, and AI grading.

11 mark
2026
If 5 − 2i is a root of a real-coefficient polynomial, another root is:
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21 mark
2026
The real quadratic with roots ±2i is:
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3Find2 marks
2026
A polynomial with real coefficients has root 4 − 3i. Write down another root and the real quadratic factor.
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41 mark
2026
(3 cis(π/5))² = ?
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51 mark
2026
Before using De Moivre on (2 + 2i)⁵ you must first:
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6Write down1 mark
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Write down the third root.
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7Find3 marks
2026
Find (2 cis(π/4))⁴, giving your answer in Cartesian form.
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81 mark
2026
The five fifth-roots of a complex number are spaced apart by:
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91 mark
2026
The fourth roots of −16 have modulus:
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101 mark
2026
On an Argand diagram, the six sixth-roots of a number form a:
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11Write down1 mark
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Write down the angle between adjacent roots on the Argand diagram.
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12Find2 marks
2026
Given z = 2 cis(π/12), find z⁶ in Cartesian form.
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131 mark
2026
(cis θ)⁻¹ equals:
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141 mark
2026
(2 cis(π/3))³ in Cartesian form is:
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15Find3 marks
2026
Find the three cube roots of 27, in polar form.
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16Find3 marks
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Find the fourth roots of 16, in polar form (−π < θ ≤ π).
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171 mark
2026
The square roots of 9 cis(π/3) are:
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18Show that2 marks
2026
Show that is also a root.
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19Explain1 mark
2026
Explain why they lie on a circle, equally spaced.
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20Find2 marks
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Given that 3i is a root of a quadratic with real coefficients, find the quadratic.
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