# How to Find the Cube Roots of a Complex Number Example with -1 + sqrt(3)*i | Summary and Q&A

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November 1, 2020
by
The Math Sorcerer
How to Find the Cube Roots of a Complex Number Example with -1 + sqrt(3)*i

## TL;DR

This video explains the process of finding the cube roots of a complex number in trigonometric form.

## Key Insights

• 💁 Complex numbers can be represented in trigonometric form using the modulus and argument.
• #️⃣ The modulus of a complex number can be calculated using the formula sqrt(x^2 + y^2).
• ⭕ The argument of a complex number can be determined by reasoning and referencing the unit circle.
• 🫚 The formula for finding the roots of a complex number includes the cube root of the modulus and the argument divided by the desired root (e.g., 3 for cube roots).
• 😉 The distinct roots can be obtained by varying the value of k in the formula.
• 😑 Writing complex numbers in trigonometric form allows for the expression of roots involving trigonometric functions.
• 🫚 The process of finding the roots of a complex number requires careful calculations and attention to detail.

## Transcript

hi everyone in this problem we're going to find the cube roots of this complex number so in order to find the roots of a complex number the very first step is to write it in what's called trigonometric form or polar form so let's go ahead and do that first and then there's a formula we can use that will allow us to find the roots we're also going t... Read More

### Q: What is the first step in finding the cube roots of a complex number?

The first step is to write the complex number in trigonometric form, using the formula r(cosθ + isinθ).

### Q: How can the modulus of a complex number be found?

The modulus can be found using the formula sqrt(x^2 + y^2), where x and y are the real and imaginary parts of the complex number.

### Q: How is the argument of a complex number determined?

The argument can be reasoned by referencing the unit circle and identifying the corresponding angle based on the real and imaginary parts.

### Q: What is the formula for finding the roots of a complex number?

The formula is z_k = (n√r) * [cos(θ/n + 2kπ/n) + isin(θ/n + 2kπ/n)], where n is the desired root (e.g., 3 for cube roots) and k represents the distinct roots.

## Summary & Key Takeaways

• The first step in finding the roots of a complex number is to write it in trigonometric form, using the formula r(cosθ + isinθ).

• The modulus (r) can be found using the formula sqrt(x^2 + y^2), where x and y are the real and imaginary parts of the complex number.

• The argument (θ) can be determined by reasoning and referencing the unit circle.

• The roots can be found using the formula z_k = (n√r) * [cos(θ/n + 2kπ/n) + isin(θ/n + 2kπ/n)], where n is the desired root (e.g., 3 for cube roots) and k represents the distinct roots.