Math Problem Statement

Écrivez le nombre complexe suivant: z = \frac{(1+i)^8 (2-2i)^6}{(1 - \sqrt{3} i)^{10}} sous la forme z = r e^{i\theta}. Donnez la valeur r et de \theta.

Solution

The image shows a problem asking to express the given complex number zz in polar form z=reiθz = r e^{i\theta}, where:

z=(1+i)8(22i)6(13i)10z = \frac{(1+i)^8 (2-2i)^6}{(1 - \sqrt{3} i)^{10}}

Steps to solve:

  1. Expressing the complex numbers in polar form:

    • 1+i1 + i:

      • In polar form, this is 2eiπ4\sqrt{2} e^{i\frac{\pi}{4}} because the modulus is 12+12=2\sqrt{1^2 + 1^2} = \sqrt{2} and the argument is π4\frac{\pi}{4} (45 degrees).
      • Therefore, (1+i)8=(2)8ei8π4=16ei2π(1+i)^8 = (\sqrt{2})^8 e^{i \cdot 8 \cdot \frac{\pi}{4}} = 16 e^{i 2\pi}.
    • 22i2 - 2i:

      • In polar form, this is 22eiπ42\sqrt{2} e^{-i \frac{\pi}{4}}, since the modulus is 22+(2)2=22\sqrt{2^2 + (-2)^2} = 2\sqrt{2} and the argument is π4-\frac{\pi}{4}.
      • Therefore, (22i)6=(22)6ei6π4=648ei3π2(2 - 2i)^6 = (2\sqrt{2})^6 e^{-i 6 \cdot \frac{\pi}{4}} = 64 \cdot 8 e^{-i \frac{3\pi}{2}}.
    • 13i1 - \sqrt{3} i:

      • In polar form, this is 2eiπ32 e^{-i \frac{\pi}{3}} since the modulus is 12+(3)2=2\sqrt{1^2 + (\sqrt{3})^2} = 2 and the argument is π3-\frac{\pi}{3}.
      • Therefore, (13i)10=210ei10π3=1024ei10π3(1 - \sqrt{3} i)^{10} = 2^{10} e^{-i 10 \cdot \frac{\pi}{3}} = 1024 e^{-i \frac{10\pi}{3}}.
  2. Simplifying zz:

    • Combine the modulus terms: z=165121024=8|z| = \frac{16 \cdot 512}{1024} = 8
    • Combine the argument terms (angles): arg(z)=2π3π2+10π3=2π3π2+10π3\arg(z) = 2\pi - \frac{3\pi}{2} + \frac{10\pi}{3} = 2\pi - \frac{3\pi}{2} + \frac{10\pi}{3} Simplifying the argument: 2π3π2+10π3=12π69π6+20π6=23π62\pi - \frac{3\pi}{2} + \frac{10\pi}{3} = \frac{12\pi}{6} - \frac{9\pi}{6} + \frac{20\pi}{6} = \frac{23\pi}{6}
  3. Final form: z=8ei23π6z = 8 e^{i \frac{23\pi}{6}}

    The polar form of zz is: r=8,θ=23π6r = 8, \quad \theta = \frac{23\pi}{6}

Would you like a more detailed explanation of any step?


Here are five related questions you might explore:

  1. How can you convert a complex number from Cartesian to polar form?
  2. What is the general formula for multiplying and dividing complex numbers in polar form?
  3. What is the significance of the modulus and argument in the polar representation of complex numbers?
  4. How can you simplify complex numbers when their argument exceeds 2π2\pi?
  5. How does De Moivre's Theorem apply to powers of complex numbers?

Tip: When working with complex numbers, always ensure to express the modulus and argument clearly for accurate results.

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Math Problem Analysis

Mathematical Concepts

Complex Numbers
Polar Form
Exponential Form

Formulas

z = r e^{i\theta}
|z| = \sqrt{x^2 + y^2} (modulus)
arg(z) = \text{angle of complex number} (argument)

Theorems

De Moivre's Theorem
Euler's Formula

Suitable Grade Level

Grade 11-12