Applicare la formula: $\frac{a}{\frac{b}{c}}$$=\frac{ac}{b}$, dove $a=1$, $b=\sin\left(x\right)$, $c=\cos\left(x\right)$, $a/b/c=\frac{1}{\frac{\sin\left(x\right)}{\cos\left(x\right)}}$ e $b/c=\frac{\sin\left(x\right)}{\cos\left(x\right)}$

Applicare la formula: $b\cdot dy=a\cdot dx$$\to \int bdy=\int adx$, dove $a=\cot\left(x\right)$, $b=\frac{e^y}{e^y+1}$, $dyb=dxa=\frac{e^y}{e^y+1}dy=\cot\left(x\right)\cdot dx$, $dyb=\frac{e^y}{e^y+1}dy$ e $dxa=\cot\left(x\right)\cdot dx$