Solution
= Solution
Along real $z=x\uparrow1$, the <modulus> is $1/(1+x^2)$ and stays bounded, but along $z=iy$ with $y\uparrow1$ it is $1/(1-y^2)\to\infty$. Since $\limsup|a_n|^{1/n}=1$, $R=1$.
= Solution
Along real $z=x\uparrow1$, the <modulus> is $1/(1+x^2)$ and stays bounded, but along $z=iy$ with $y\uparrow1$ it is $1/(1-y^2)\to\infty$. Since $\limsup|a_n|^{1/n}=1$, $R=1$.