I already found the radius of convergence for the power series $\sum_{n=0}^{\infty}\cos(n)z^n$ to be $R=1$. It is really messy and uses the squeeze theorem and the Cauchy–Hadamard theorem. Has anyone a nice and short proof for my problem? Is there maybe another way without the theorems I used?
2026-05-05 03:32:57.1777951977
Radius of convergence of $\sum_{n=0}^{\infty}\cos(n)z^n$
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