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Let $f$ a entire function: $f(R)\subset R.\;$ Prove that $f(\bar{z})=\overline{f(z)}, \forall z\in C$

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up vote 6 down vote accepted

The function $g(z):=\overline{f(\bar{z})}$ is also entire. By assumption, it coincides with $f$ on $\mathbb{R}$. By the principle of isolated zeroes, it follows that $f=g$ on $\mathbb{C}$.

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Clean and elegant. +1 – ncmathsadist Jan 10 '13 at 0:00
Sorry i don't understand, would you explain more – erfan soheil Dec 15 '14 at 11:30

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