Math Problem Statement

Find the polar form of z = −1 + j√3. Hence, find z^10.

Solution

To find the polar form of the complex number z=1+j3z = -1 + j\sqrt{3}, we'll follow these steps:

Step 1: Calculate the magnitude rr

The magnitude rr of a complex number z=x+jyz = x + jy is given by:

r=x2+y2r = \sqrt{x^2 + y^2}

For z=1+j3z = -1 + j\sqrt{3}, we have x=1x = -1 and y=3y = \sqrt{3}. Therefore:

r=(1)2+(3)2=1+3=4=2r = \sqrt{(-1)^2 + (\sqrt{3})^2} = \sqrt{1 + 3} = \sqrt{4} = 2

Step 2: Calculate the argument θ\theta

The argument θ\theta is found using:

θ=tan1(yx)\theta = \tan^{-1}\left(\frac{y}{x}\right)

Since x=1x = -1 and y=3y = \sqrt{3}, the argument θ\theta is:

θ=tan1(31)\theta = \tan^{-1}\left(\frac{\sqrt{3}}{-1}\right)

This angle lies in the second quadrant (because xx is negative and yy is positive), so we need to add π\pi to the reference angle:

θ=ππ3=2π3\theta = \pi - \frac{\pi}{3} = \frac{2\pi}{3}

Step 3: Write the polar form of zz

The polar form of the complex number z=1+j3z = -1 + j\sqrt{3} is:

z=2(cos2π3+jsin2π3)z = 2 \left( \cos \frac{2\pi}{3} + j\sin \frac{2\pi}{3} \right)

Step 4: Find z10z^{10}

Using De Moivre's Theorem, which states:

zn=rn(cos(nθ)+jsin(nθ))z^n = r^n \left( \cos(n\theta) + j\sin(n\theta) \right)

For z10z^{10}:

z10=210(cos(10×2π3)+jsin(10×2π3))z^{10} = 2^{10} \left( \cos\left(10 \times \frac{2\pi}{3}\right) + j\sin\left(10 \times \frac{2\pi}{3}\right) \right)

Simplifying 2102^{10} and the angle:

z10=1024(cos(20π3)+jsin(20π3))z^{10} = 1024 \left( \cos\left(\frac{20\pi}{3}\right) + j\sin\left(\frac{20\pi}{3}\right) \right)

Since 20π3\frac{20\pi}{3} is equivalent to 2π3\frac{2\pi}{3} after reducing modulo 2π2\pi:

z10=1024(cos2π3+jsin2π3)z^{10} = 1024 \left( \cos\frac{2\pi}{3} + j\sin\frac{2\pi}{3} \right)

Using the known values:

cos2π3=12,sin2π3=32\cos\frac{2\pi}{3} = -\frac{1}{2}, \quad \sin\frac{2\pi}{3} = \frac{\sqrt{3}}{2}

Thus:

z10=1024(12+j32)z^{10} = 1024 \left(-\frac{1}{2} + j\frac{\sqrt{3}}{2}\right)

Finally:

z10=512+j5123z^{10} = -512 + j512\sqrt{3}

This is the value of z10z^{10}.

Would you like any further details on this calculation or have any questions?

Related Questions:

  1. How do you convert a complex number from polar to rectangular form?
  2. What is the geometric interpretation of raising a complex number to a power?
  3. How would the calculation change if z=1j3z = 1 - j\sqrt{3}?
  4. Can you derive the polar form for any general complex number z=x+jyz = x + jy?
  5. What are the implications of the polar form when dealing with complex roots?

Tip:

When working with complex numbers in polar form, always reduce the argument (angle) modulo 2π2\pi to simplify your calculations.

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Math Problem Analysis

Mathematical Concepts

Complex Numbers
Polar Form
De Moivre's Theorem

Formulas

Magnitude of a Complex Number
Argument of a Complex Number
De Moivre's Theorem

Theorems

De Moivre's Theorem

Suitable Grade Level

Advanced High School