Se da una serie:
$$\frac{\log{\left(n \right)} + \operatorname{atan}{\left(n \right)}}{n^{\frac{4}{3}} + \cos^{2}{\left(n \right)}}$$
Es la serie del tipo
$$a_{n} \left(c x - x_{0}\right)^{d n}$$
- serie de potencias.
El radio de convergencia de la serie de potencias puede calcularse por la fórmula:
$$R^{d} = \frac{x_{0} + \lim_{n \to \infty} \left|{\frac{a_{n}}{a_{n + 1}}}\right|}{c}$$
En nuestro caso
$$a_{n} = \frac{\log{\left(n \right)} + \operatorname{atan}{\left(n \right)}}{n^{\frac{4}{3}} + \cos^{2}{\left(n \right)}}$$
y
$$x_{0} = 0$$
,
$$d = 0$$
,
$$c = 1$$
entonces
$$1 = \lim_{n \to \infty}\left(\frac{\left(\left(n + 1\right)^{\frac{4}{3}} + \cos^{2}{\left(n + 1 \right)}\right) \left|{\log{\left(n \right)} + \operatorname{atan}{\left(n \right)}}\right|}{\left(n^{\frac{4}{3}} + \cos^{2}{\left(n \right)}\right) \left(\log{\left(n + 1 \right)} + \operatorname{atan}{\left(n + 1 \right)}\right)}\right)$$
Tomamos como el límitehallamos
$$R^{0} = \lim_{n \to \infty}\left(\frac{\left(\left(n + 1\right)^{\frac{4}{3}} + \cos^{2}{\left(n + 1 \right)}\right) \left|{\log{\left(n \right)} + \operatorname{atan}{\left(n \right)}}\right|}{\left(n^{\frac{4}{3}} + \cos^{2}{\left(n \right)}\right) \left(\log{\left(n + 1 \right)} + \operatorname{atan}{\left(n + 1 \right)}\right)}\right)$$