Math Problem Statement

Find the product z₁z₂ and the quotient z₁/z₂. Express your answers in polar form. z₁ = cos(7π/8) + i sin(7π/8), z₂ = cos(π/4) + i sin(π/4).

Solution

The problem involves finding the product z1z2z_1 z_2 and the quotient z1z2\frac{z_1}{z_2} for the given complex numbers in polar form.

The given complex numbers are: z1=cos(7π8)+isin(7π8),z_1 = \cos\left(\frac{7\pi}{8}\right) + i\sin\left(\frac{7\pi}{8}\right), z2=cos(π4)+isin(π4).z_2 = \cos\left(\frac{\pi}{4}\right) + i\sin\left(\frac{\pi}{4}\right).

In polar form, a complex number z=cosθ+isinθz = \cos\theta + i\sin\theta is written as eiθe^{i\theta}.

Converting to polar exponential form:

z1=ei7π8,z2=eiπ4.z_1 = e^{i\frac{7\pi}{8}}, \quad z_2 = e^{i\frac{\pi}{4}}.

1. Finding the product z1z2z_1 z_2:

The product of two complex numbers in polar form is obtained by adding their angles: z1z2=ei7π8eiπ4=ei(7π8+π4).z_1 z_2 = e^{i\frac{7\pi}{8}} \cdot e^{i\frac{\pi}{4}} = e^{i\left(\frac{7\pi}{8} + \frac{\pi}{4}\right)}.

Simplify the angle: 7π8+π4=7π8+2π8=9π8.\frac{7\pi}{8} + \frac{\pi}{4} = \frac{7\pi}{8} + \frac{2\pi}{8} = \frac{9\pi}{8}.

Thus: z1z2=ei9π8.z_1 z_2 = e^{i\frac{9\pi}{8}}.

In polar form: z1z2=cos(9π8)+isin(9π8).z_1 z_2 = \cos\left(\frac{9\pi}{8}\right) + i\sin\left(\frac{9\pi}{8}\right).

2. Finding the quotient z1z2\frac{z_1}{z_2}:

The quotient of two complex numbers in polar form is obtained by subtracting their angles: z1z2=ei7π8eiπ4=ei(7π8π4).\frac{z_1}{z_2} = \frac{e^{i\frac{7\pi}{8}}}{e^{i\frac{\pi}{4}}} = e^{i\left(\frac{7\pi}{8} - \frac{\pi}{4}\right)}.

Simplify the angle: 7π8π4=7π82π8=5π8.\frac{7\pi}{8} - \frac{\pi}{4} = \frac{7\pi}{8} - \frac{2\pi}{8} = \frac{5\pi}{8}.

Thus: z1z2=ei5π8.\frac{z_1}{z_2} = e^{i\frac{5\pi}{8}}.

In polar form: z1z2=cos(5π8)+isin(5π8).\frac{z_1}{z_2} = \cos\left(\frac{5\pi}{8}\right) + i\sin\left(\frac{5\pi}{8}\right).

Final Answers:

  1. z1z2=cos(9π8)+isin(9π8)z_1 z_2 = \cos\left(\frac{9\pi}{8}\right) + i\sin\left(\frac{9\pi}{8}\right).
  2. z1z2=cos(5π8)+isin(5π8)\frac{z_1}{z_2} = \cos\left(\frac{5\pi}{8}\right) + i\sin\left(\frac{5\pi}{8}\right).

Let me know if you would like a detailed step-by-step breakdown of any part!

Here are five related questions:

  1. What are the magnitudes of z1z_1 and z2z_2?
  2. How do you convert between rectangular and polar forms of complex numbers?
  3. Can you plot z1z_1 and z2z_2 on the complex plane?
  4. What happens to the angles in polar form when you compute powers of complex numbers?
  5. How do you find the conjugate of a complex number in polar form?

Tip: When multiplying or dividing complex numbers in polar form, remember that you only need to work with the angles—magnitudes are multiplied for products and divided for quotients.

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Math Problem Analysis

Mathematical Concepts

Complex Numbers
Polar Form
Multiplication and Division of Complex Numbers

Formulas

z₁z₂ = e^(iθ₁) * e^(iθ₂) = e^(i(θ₁ + θ₂))
z₁/z₂ = e^(iθ₁) / e^(iθ₂) = e^(i(θ₁ - θ₂))
Polar form of complex numbers: z = cos(θ) + i sin(θ)

Theorems

Angle Addition and Subtraction in Polar Form

Suitable Grade Level

Grades 11-12 or College