Applicare la formula: $\int\frac{n}{x^2+b}dx$$=\frac{n}{\sqrt{b}}\arctan\left(\frac{x}{\sqrt{b}}\right)+C$, dove $b=\frac{2}{5}$ e $n=1$

Applicare la formula: $\left[x\right]_{a}^{b}$$=eval\left(x,b\right)-eval\left(x,a\right)+C$, dove $a=0$, $b=4$ e $x=\frac{1}{\sqrt{0.4}}\arctan\left(\frac{x}{\sqrt{0.4}}\right)$