Math Problem Statement

(Sq root3-i)^4

Solution

To solve (3i)4(\sqrt{3} - i)^4, we can use De Moivre's Theorem, which is useful when raising complex numbers to a power. Here's the step-by-step process:

  1. Convert the complex number to polar form:
    A complex number z=a+biz = a + bi can be represented in polar form as: z=r(cosθ+isinθ)z = r(\cos \theta + i \sin \theta) where r=a2+b2r = \sqrt{a^2 + b^2} is the magnitude and θ=tan1(ba)\theta = \tan^{-1} \left(\frac{b}{a}\right) is the argument.

    For 3i\sqrt{3} - i:

    • a=3a = \sqrt{3}
    • b=1b = -1 r=(3)2+(1)2=3+1=4=2r = \sqrt{(\sqrt{3})^2 + (-1)^2} = \sqrt{3 + 1} = \sqrt{4} = 2 θ=tan1(13)=tan1(13)\theta = \tan^{-1}\left(\frac{-1}{\sqrt{3}}\right) = \tan^{-1}\left(-\frac{1}{\sqrt{3}}\right)

    Since tan1(13)=π6\tan^{-1}\left(\frac{1}{\sqrt{3}}\right) = \frac{\pi}{6}, and the point lies in the fourth quadrant: θ=π6\theta = -\frac{\pi}{6} So, in polar form: 3i=2(cos(π6)+isin(π6))\sqrt{3} - i = 2 \left( \cos\left(-\frac{\pi}{6}\right) + i \sin\left(-\frac{\pi}{6}\right) \right)

  2. Apply De Moivre's Theorem:
    zn=rn(cos(nθ)+isin(nθ))z^n = r^n \left( \cos(n\theta) + i\sin(n\theta) \right) Substituting r=2r = 2, θ=π6\theta = -\frac{\pi}{6}, and n=4n = 4: (3i)4=24(cos(4×π6)+isin(4×π6))(\sqrt{3} - i)^4 = 2^4 \left( \cos\left(4 \times -\frac{\pi}{6}\right) + i \sin\left(4 \times -\frac{\pi}{6}\right) \right) =16(cos(4π6)+isin(4π6))= 16 \left( \cos\left(-\frac{4\pi}{6}\right) + i \sin\left(-\frac{4\pi}{6}\right) \right) Simplify the angle: =16(cos(2π3)+isin(2π3))= 16 \left( \cos\left(-\frac{2\pi}{3}\right) + i \sin\left(-\frac{2\pi}{3}\right) \right)

  3. Evaluate the trigonometric functions:
    cos(2π3)=12,sin(2π3)=32\cos\left(-\frac{2\pi}{3}\right) = -\frac{1}{2}, \quad \sin\left(-\frac{2\pi}{3}\right) = -\frac{\sqrt{3}}{2} Therefore: (3i)4=16(12i32)(\sqrt{3} - i)^4 = 16 \left( -\frac{1}{2} - i\frac{\sqrt{3}}{2} \right) =16(12i32)=883i= 16 \left( -\frac{1}{2} - i\frac{\sqrt{3}}{2} \right) = -8 - 8\sqrt{3}i

So, the result is: (3i)4=883i(\sqrt{3} - i)^4 = -8 - 8\sqrt{3}i

Would you like further details or have any questions?

Here are five questions related to this topic:

  1. How does De Moivre's Theorem help in simplifying powers of complex numbers?
  2. What is the significance of the polar form of a complex number?
  3. How do you determine which quadrant a complex number lies in?
  4. What are the steps to convert a complex number from rectangular to polar form?
  5. How does the argument of a complex number change when raised to a power?

Tip: When working with complex numbers, always check the quadrant to ensure correct angle measurements.

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Math Problem Analysis

Mathematical Concepts

Complex Numbers
De Moivre's Theorem

Formulas

De Moivre's Theorem

Theorems

De Moivre's Theorem

Suitable Grade Level

Advanced High School