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

Applicare la formula: $\frac{\frac{a}{b}}{c}$$=\frac{a}{bc}$, dove $a=1-\cos\left(x\right)$, $b=\cos\left(x\right)$, $c=x^3$, $a/b/c=\frac{\frac{1-\cos\left(x\right)}{\cos\left(x\right)}}{x^3}$ e $a/b=\frac{1-\cos\left(x\right)}{\cos\left(x\right)}$