Integral de $$$\frac{f^{2}}{f^{2} + 1}$$$

Halla $$$\int \frac{f^{2}}{f^{2} + 1}\, df$$$.

Reescribe y separa la fracción:

$${\color{red}{\int{\frac{f^{2}}{f^{2} + 1} d f}}} = {\color{red}{\int{\left(1 - \frac{1}{f^{2} + 1}\right)d f}}}$$

Integra término a término:

$${\color{red}{\int{\left(1 - \frac{1}{f^{2} + 1}\right)d f}}} = {\color{red}{\left(\int{1 d f} - \int{\frac{1}{f^{2} + 1} d f}\right)}}$$

Aplica la regla de la constante $$$\int c\, df = c f$$$ con $$$c=1$$$:

$$- \int{\frac{1}{f^{2} + 1} d f} + {\color{red}{\int{1 d f}}} = - \int{\frac{1}{f^{2} + 1} d f} + {\color{red}{f}}$$

La integral de $$$\frac{1}{f^{2} + 1}$$$ es $$$\int{\frac{1}{f^{2} + 1} d f} = \operatorname{atan}{\left(f \right)}$$$:

$$f - {\color{red}{\int{\frac{1}{f^{2} + 1} d f}}} = f - {\color{red}{\operatorname{atan}{\left(f \right)}}}$$

Por lo tanto,

$$\int{\frac{f^{2}}{f^{2} + 1} d f} = f - \operatorname{atan}{\left(f \right)}$$

Añade la constante de integración:

$$\int{\frac{f^{2}}{f^{2} + 1} d f} = f - \operatorname{atan}{\left(f \right)}+C$$

$$$\int \frac{f^{2}}{f^{2} + 1}\, df = \left(f - \operatorname{atan}{\left(f \right)}\right) + C$$$A