Complex number and power series

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SUMMARY

The discussion focuses on finding the power series for the expression e^z + e^(ωz) + e^((ω^2)z), where ω is defined as e^(2πi/3). Participants emphasize the importance of utilizing the equation 1 + ω + ω^2 = 0 to simplify the coefficients in the power series. The solution involves writing the series as a sum of (z^n)*(1 + ω^n + ω^(2n))/n! for n from 0 to infinity. Analyzing specific cases for n=0, 1, 2, and 3 is recommended to facilitate generalization of the solution.

PREREQUISITES
  • Understanding of complex numbers, specifically the properties of e^(iθ).
  • Familiarity with power series expansions and their convergence.
  • Knowledge of the roots of unity, particularly the cube roots.
  • Basic skills in algebraic manipulation of series and summations.
NEXT STEPS
  • Explore the derivation of power series for exponential functions.
  • Study the properties and applications of complex roots of unity.
  • Learn about the convergence criteria for power series.
  • Investigate the use of Taylor series in complex analysis.
USEFUL FOR

Students and educators in mathematics, particularly those studying complex analysis and power series, as well as anyone seeking to deepen their understanding of exponential functions in the context of complex numbers.

rainwyz0706
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Homework Statement



Let ω be the complex number e^(2πi/3), Find the power series for e^z + e^(ωz) + e^((ω^2) z).




Homework Equations





The Attempt at a Solution


I can show that 1+w+w^2=0, don't know if it would help. Could anyone please give me some hints? Any input is appreciated!
 
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Write out the three individual power series and sum them. Collect like powers of z. Use your equation for w to try and simplify the coefficients.
 
I can write it as the sum of (z^n)*(1+w^n+w^2n)/n!, n from 0 to infinity. But I'm still not sure how to simplify 1+w^n+w^2n from 1+w+w^2=0. Could you explain it in a bit more details? Thanks a lot!
 
rainwyz0706 said:
I can write it as the sum of (z^n)*(1+w^n+w^2n)/n!, n from 0 to infinity. But I'm still not sure how to simplify 1+w^n+w^2n from 1+w+w^2=0. Could you explain it in a bit more details? Thanks a lot!

Look at the n=0,1,2,3 cases. Hint, what's w^3? Once you've got those you should find it pretty easy to generalize.
 
thanks, I got it!
 

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