Math Problem Statement
Consider the following complex number: w = (1 - √3i)^5 / (1 + i)^4. (a) Express w in Cartesian form and in polar form.
Solution
Let's analyze the complex number given by the expression:
Step 1: Express in Polar Form
Denominator:
To express in polar form, we calculate its modulus and argument .
-
Modulus:
-
Argument:
Thus, in polar form: where "cis" stands for .
Now raise this to the 4th power:
Numerator:
Similarly, express in polar form.
-
Modulus:
-
Argument:
Thus, in polar form:
Now raise this to the 5th power:
Step 2: Combine to Find
Now, combine the numerator and denominator:
= -8 \text{cis} \left(-\frac{5\pi}{3} - \pi\right) = -8 \text{cis} \left(-\frac{8\pi}{3}\right)$$ Since the argument $$-\frac{8\pi}{3}$$ is coterminal with $$\frac{4\pi}{3}$$, we have: $$w = -8 \text{cis} \frac{4\pi}{3}$$ Thus, the polar form of $$w$$ is: $$w = 8 \text{cis} \left( \frac{4\pi}{3} \right)$$ ### Step 3: Convert to Cartesian Form To convert back to Cartesian form, use the definition of "cis": $$w = 8 \left( \cos \frac{4\pi}{3} + i \sin \frac{4\pi}{3} \right)$$ We know: $$\cos \frac{4\pi}{3} = -\frac{1}{2}, \quad \sin \frac{4\pi}{3} = -\frac{\sqrt{3}}{2}$$ Thus: $$w = 8 \left( -\frac{1}{2} - i \frac{\sqrt{3}}{2} \right) = -4 - 4\sqrt{3}i$$ ### Final Answer: - **Polar form:** $$w = 8 \text{cis} \left( \frac{4\pi}{3} \right)$$ - **Cartesian form:** $$w = -4 - 4\sqrt{3}i$$ Would you like further details or have any specific questions? Here are 5 questions related to this problem: 1. How do you calculate the modulus and argument of a complex number? 2. Why do we use polar form to simplify powers of complex numbers? 3. What does "cis" mean in polar form? 4. How do arguments change when raising a complex number to a power? 5. Why is the argument in the final polar form expressed as $$\frac{4\pi}{3}$$? **Tip:** When converting between Cartesian and polar forms, always verify your calculations of the modulus and argument to ensure accuracy.Ask a new question for Free
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Math Problem Analysis
Mathematical Concepts
Complex Numbers
Polar Coordinates
Powers of Complex Numbers
Formulas
Polar form: z = r(cos θ + i sin θ) or r cis θ
Modulus: |z| = √(a^2 + b^2) for z = a + bi
Argument: θ = tan⁻¹(b/a) for z = a + bi
Multiplication and exponentiation of complex numbers in polar form
Theorems
De Moivre's Theorem
Suitable Grade Level
Undergraduate Mathematics