Find (-1+ i)"and write the answer in exact polar form and rectangular form.
Trigonometry (MindTap Course List)
10th Edition
ISBN:9781337278461
Author:Ron Larson
Publisher:Ron Larson
Chapter4: Complex Numbers
Section: Chapter Questions
Problem 7T
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![**Problem Statement:**
Find \(( -1 + i )^6\) and write the answer in exact polar form and rectangular form.
**Solution:**
To solve the given problem, we will convert the complex number \( -1 + i \) to its polar form and then use De Moivre’s Theorem to find the desired power. Finally, we will convert the answer back to rectangular form.
### Step 1: Convert \( -1 + i \) to Polar Form
A complex number \( z \) in rectangular form is expressed as \( z = x + yi \), where \( x \) and \( y \) are real numbers. For \( -1 + i \):
- \( x = -1 \)
- \( y = 1 \)
The polar form is \( r (\cos \theta + i \sin \theta) \), where:
- \( r \) is the modulus of the complex number, found using \( r = \sqrt{x^2 + y^2} \).
- \( \theta \) is the argument (angle) of the complex number, found using \( \tan \theta = \frac{y}{x} \).
Calculate the modulus \( r \):
\[ r = \sqrt{(-1)^2 + (1)^2} = \sqrt{1 + 1} = \sqrt{2} \]
Calculate the argument \( \theta \):
\[ \tan \theta = \frac{1}{-1} = -1 \]
\[ \theta = \tan^{-1}(-1) \]
Since the complex number \( -1 + i \) is in the second quadrant, we have:
\[ \theta = \pi - \frac{\pi}{4} = \frac{3\pi}{4} \]
Therefore, the polar form of \( -1 + i \) is:
\[ \sqrt{2} \left( \cos \frac{3\pi}{4} + i \sin \frac{3\pi}{4} \right) \]
### Step 2: Apply De Moivre's Theorem to Find \(( -1 + i )^6\)
Using De Moivre’s Theorem \( \left( r (\cos \theta + i \sin \theta) \right)^n = r^n (\cos n\theta + i \sin n\theta) \):
Let \( n =](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F5e4013eb-babb-4770-9243-fb3338b3d4a1%2F86253f4c-45f8-4fea-8eed-121f1f90d72a%2Forc5bhr.jpeg&w=3840&q=75)
Transcribed Image Text:**Problem Statement:**
Find \(( -1 + i )^6\) and write the answer in exact polar form and rectangular form.
**Solution:**
To solve the given problem, we will convert the complex number \( -1 + i \) to its polar form and then use De Moivre’s Theorem to find the desired power. Finally, we will convert the answer back to rectangular form.
### Step 1: Convert \( -1 + i \) to Polar Form
A complex number \( z \) in rectangular form is expressed as \( z = x + yi \), where \( x \) and \( y \) are real numbers. For \( -1 + i \):
- \( x = -1 \)
- \( y = 1 \)
The polar form is \( r (\cos \theta + i \sin \theta) \), where:
- \( r \) is the modulus of the complex number, found using \( r = \sqrt{x^2 + y^2} \).
- \( \theta \) is the argument (angle) of the complex number, found using \( \tan \theta = \frac{y}{x} \).
Calculate the modulus \( r \):
\[ r = \sqrt{(-1)^2 + (1)^2} = \sqrt{1 + 1} = \sqrt{2} \]
Calculate the argument \( \theta \):
\[ \tan \theta = \frac{1}{-1} = -1 \]
\[ \theta = \tan^{-1}(-1) \]
Since the complex number \( -1 + i \) is in the second quadrant, we have:
\[ \theta = \pi - \frac{\pi}{4} = \frac{3\pi}{4} \]
Therefore, the polar form of \( -1 + i \) is:
\[ \sqrt{2} \left( \cos \frac{3\pi}{4} + i \sin \frac{3\pi}{4} \right) \]
### Step 2: Apply De Moivre's Theorem to Find \(( -1 + i )^6\)
Using De Moivre’s Theorem \( \left( r (\cos \theta + i \sin \theta) \right)^n = r^n (\cos n\theta + i \sin n\theta) \):
Let \( n =
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