Math Problem Statement

Express z^3 * w^-1 in standard polar form, where z = sqrt(3)/2 + (1/2)i and w = -(1/sqrt(2)) + (1/sqrt(2))i.

Solution

We are asked to express z3w1z^3 w^{-1} in standard polar form, given:

z=32+12iandw=12+12i.z = \frac{\sqrt{3}}{2} + \frac{1}{2}i \quad \text{and} \quad w = -\frac{1}{\sqrt{2}} + \frac{1}{\sqrt{2}}i.

Step 1: Convert zz and ww to polar form.

z=32+12iz = \frac{\sqrt{3}}{2} + \frac{1}{2}i:

  • The modulus z|z| is: z=(32)2+(12)2=34+14=1=1.|z| = \sqrt{\left(\frac{\sqrt{3}}{2}\right)^2 + \left(\frac{1}{2}\right)^2} = \sqrt{\frac{3}{4} + \frac{1}{4}} = \sqrt{1} = 1.
  • The argument arg(z)\arg(z) is: θz=tan1(1232)=tan1(13)=π6.\theta_z = \tan^{-1}\left(\frac{\frac{1}{2}}{\frac{\sqrt{3}}{2}}\right) = \tan^{-1}\left(\frac{1}{\sqrt{3}}\right) = \frac{\pi}{6}. So, z=cis(π6)z = \text{cis}\left(\frac{\pi}{6}\right).

w=12+12iw = -\frac{1}{\sqrt{2}} + \frac{1}{\sqrt{2}}i:

  • The modulus w|w| is: w=(12)2+(12)2=12+12=1=1.|w| = \sqrt{\left(-\frac{1}{\sqrt{2}}\right)^2 + \left(\frac{1}{\sqrt{2}}\right)^2} = \sqrt{\frac{1}{2} + \frac{1}{2}} = \sqrt{1} = 1.
  • The argument arg(w)\arg(w) is: θw=tan1(1212)=tan1(1)=3π4.\theta_w = \tan^{-1}\left(\frac{\frac{1}{\sqrt{2}}}{-\frac{1}{\sqrt{2}}}\right) = \tan^{-1}(-1) = \frac{3\pi}{4}. So, w=cis(3π4)w = \text{cis}\left(\frac{3\pi}{4}\right).

Step 2: Calculate z3z^3:

z3=[cis(π6)]3=cis(3×π6)=cis(π2).z^3 = \left[\text{cis}\left(\frac{\pi}{6}\right)\right]^3 = \text{cis}\left(3 \times \frac{\pi}{6}\right) = \text{cis}\left(\frac{\pi}{2}\right).

Step 3: Calculate w1w^{-1}:

w1=[cis(3π4)]1=cis(3π4).w^{-1} = \left[\text{cis}\left(\frac{3\pi}{4}\right)\right]^{-1} = \text{cis}\left(-\frac{3\pi}{4}\right).

Step 4: Multiply z3z^3 and w1w^{-1}:

z3w1=cis(π2+(3π4))=cis(π23π4)=cis(π4).z^3 w^{-1} = \text{cis}\left(\frac{\pi}{2} + \left(-\frac{3\pi}{4}\right)\right) = \text{cis}\left(\frac{\pi}{2} - \frac{3\pi}{4}\right) = \text{cis}\left(-\frac{\pi}{4}\right).

Thus, z3w1=cos(π4)+isin(π4)z^3 w^{-1} = \cos\left(-\frac{\pi}{4}\right) + i \sin\left(-\frac{\pi}{4}\right).

Answer:

The correct option is: cos(π4)+isin(π4).\boxed{\cos\left(-\frac{\pi}{4}\right) + i \sin\left(-\frac{\pi}{4}\right)}.

Do you want more details or have any other questions? Here are 5 related questions to explore:

  1. How do you convert a complex number from rectangular form to polar form?
  2. What are the properties of complex numbers under multiplication and division in polar form?
  3. How do the modulus and argument change when raising a complex number to a power?
  4. How can you interpret the geometric meaning of multiplying two complex numbers in polar form?
  5. What is the significance of the angle θ\theta in the polar form of a complex number?

Tip: When working with complex numbers in polar form, always remember that multiplying corresponds to adding angles and dividing corresponds to subtracting angles.

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Math Problem Analysis

Mathematical Concepts

Complex Numbers
Polar Form
Exponential Form of Complex Numbers

Formulas

|z| = sqrt(x^2 + y^2)
arg(z) = tan^(-1)(y/x)
Multiplication of complex numbers in polar form: z1 * z2 = r1 * r2 * cis(theta1 + theta2)
Division of complex numbers in polar form: z1 / z2 = (r1 / r2) * cis(theta1 - theta2)

Theorems

De Moivre's Theorem
Properties of Complex Numbers in Polar Form

Suitable Grade Level

Grades 11-12