Euler's Method of Trigonometric Series- Real Analysis

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SUMMARY

The discussion focuses on deriving the formula \((1-a\cos(\phi))/(1-2a\cos(\phi)+a^2) = 1 + a\cos(\phi) + a^2\cos(2\phi) + a^3\cos(3\phi) + \ldots\) using Equation (1), which is expressed as \(1/(1-a(\cos(\phi)+i\sin(\phi))) = 1 + [a(\cos(\phi)+i\sin(\phi)] + [a(\cos(\phi)+i\sin(\phi)]^2 + [a(\cos(\phi)+i\sin(\phi)]^3 + \ldots\). The key insight is the application of the identity \((\cos(\phi)+i\sin(\phi))^k = \cos(k\phi) + i\sin(k\phi)\) to facilitate the derivation.

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Homework Statement



Use Equation (1) to derive the formula: (1-a*cos(phi))/(1-2*a*cos(phi)+a^2))= 1+a*cos(phi)+a^2(cos(2phi))+a^3(cos(3phi))...


Homework Equations



Equation (1) is 1/(1-a(cos(phi)+isin(phi)))= 1+ [a(cos(phi)+isin(phi)]+ [a(cos(phi)+isin(phi)]^2 + [a(cos(phi)+isin(phi)]^3...



The Attempt at a Solution



I know that you are supposed to somehow use that (cos(phi)+isin(phi))^k= cos(kphi)+ isin(kphi), but I'm not sure how to go about this at all. Please help!
 
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