Math Problem Statement

What is answer?

If ω is a complex cube root of unity, then the value of ω^100 + ω^101 + ω^102 is?

Solution

The problem asks for the value of ω100+ω101+ω102\omega^{100} + \omega^{101} + \omega^{102}, where ω\omega is a complex cube root of unity. Let’s solve this step by step.

Properties of Cube Roots of Unity

The complex cube roots of unity are the solutions to the equation:

ω3=1\omega^3 = 1

These roots are:

  • 11 (real cube root)
  • ω\omega, where ω=e2πi/3\omega = e^{2\pi i / 3}
  • ω2=e4πi/3\omega^2 = e^{4\pi i / 3}

These roots satisfy the following relations: 1+ω+ω2=01 + \omega + \omega^2 = 0

Simplifying Powers of ω\omega

Since ω3=1\omega^3 = 1, powers of ω\omega repeat every 3 steps. Therefore:

  • ω100=ω100mod3=ω1=ω\omega^{100} = \omega^{100 \mod 3} = \omega^1 = \omega
  • ω101=ω101mod3=ω2\omega^{101} = \omega^{101 \mod 3} = \omega^2
  • ω102=ω102mod3=ω0=1\omega^{102} = \omega^{102 \mod 3} = \omega^0 = 1

Now, substitute these values into the expression: ω100+ω101+ω102=ω+ω2+1\omega^{100} + \omega^{101} + \omega^{102} = \omega + \omega^2 + 1

Using the property ω+ω2+1=0\omega + \omega^2 + 1 = 0, we find: ω100+ω101+ω102=0\omega^{100} + \omega^{101} + \omega^{102} = 0

Final Answer:

The value of ω100+ω101+ω102\omega^{100} + \omega^{101} + \omega^{102} is 00, which corresponds to option c).

Would you like more details or have any other questions?

Here are 5 related questions to expand on this concept:

  1. What are the roots of unity for other powers, such as the 4th or 5th roots of unity?
  2. How can the properties of cube roots of unity be applied to solve equations in number theory?
  3. Can you derive the general expression for the nn-th roots of unity?
  4. How are roots of unity represented geometrically in the complex plane?
  5. How does the symmetry of roots of unity help simplify polynomial equations?

Tip: The property 1+ω+ω2=01 + \omega + \omega^2 = 0 is a key identity when working with cube roots of unity, and it can greatly simplify many complex number problems.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Complex Numbers
Roots of Unity
Modular Arithmetic

Formulas

ω^3 = 1
1 + ω + ω^2 = 0

Theorems

Cube Roots of Unity Theorem
Properties of Modular Arithmetic

Suitable Grade Level

Grades 11-12