Math Problem Statement

Givet to komplekse tal z1 og z2. Det oplyses at Arg(z1) = π/4 og Arg(z2) = 3. Bestem Arg(-2z1^4/z2^10).

Solution

The problem provides two complex numbers, z1z_1 and z2z_2, with known arguments:

  1. Arg(z1)=π4\text{Arg}(z_1) = \frac{\pi}{4}
  2. Arg(z2)=3\text{Arg}(z_2) = 3

We need to find the argument of 2z14z210-2 \frac{z_1^4}{z_2^{10}}.

Solution Steps

  1. Argument of z14z_1^4: Using the property Arg(zn)=nArg(z)\text{Arg}(z^n) = n \cdot \text{Arg}(z), we get: Arg(z14)=4Arg(z1)=4π4=π.\text{Arg}(z_1^4) = 4 \cdot \text{Arg}(z_1) = 4 \cdot \frac{\pi}{4} = \pi.

  2. Argument of z210z_2^{10}: Similarly, Arg(z210)=10Arg(z2)=103=30.\text{Arg}(z_2^{10}) = 10 \cdot \text{Arg}(z_2) = 10 \cdot 3 = 30.

  3. Argument of z14z210\frac{z_1^4}{z_2^{10}}: Using the property Arg(z1z2)=Arg(z1)Arg(z2)\text{Arg}\left(\frac{z_1}{z_2}\right) = \text{Arg}(z_1) - \text{Arg}(z_2), we have: Arg(z14z210)=Arg(z14)Arg(z210)=π30=π30.\text{Arg}\left(\frac{z_1^4}{z_2^{10}}\right) = \text{Arg}(z_1^4) - \text{Arg}(z_2^{10}) = \pi - 30 = \pi - 30.

  4. Argument of 2-2: Since 2-2 is a real number and lies on the negative real axis, its argument is π\pi.

  5. Combining all arguments: Finally, the argument of 2z14z210-2 \frac{z_1^4}{z_2^{10}} is: Arg(2z14z210)=Arg(2)+Arg(z14z210)=π+(π30)=2π30.\text{Arg}\left(-2 \frac{z_1^4}{z_2^{10}}\right) = \text{Arg}(-2) + \text{Arg}\left(\frac{z_1^4}{z_2^{10}}\right) = \pi + (\pi - 30) = 2\pi - 30.

Thus, the answer is: Arg(2z14z210)=2π30.\text{Arg}\left(-2 \frac{z_1^4}{z_2^{10}}\right) = 2\pi - 30.

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Related Questions

  1. What is the argument of a product of two complex numbers?
  2. How does multiplying a complex number by a negative real number affect its argument?
  3. How do we find the argument of a complex number raised to a power?
  4. How does division affect the argument of two complex numbers?
  5. What is the significance of the principal argument in complex numbers?

Tip

Always remember that arguments in complex numbers are often considered modulo 2π2\pi to keep them within the principal range.

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Math Problem Analysis

Mathematical Concepts

Complex Numbers
Arguments of Complex Numbers
Multiplication and Division of Complex Numbers

Formulas

Arg(z^n) = n * Arg(z)
Arg(z1 / z2) = Arg(z1) - Arg(z2)
Arg(-a) = Arg(a) + π for any positive real number a

Theorems

Argument Property for Powers and Quotients of Complex Numbers

Suitable Grade Level

Grades 10-12