Applicare la formula: $x\left(a+b\right)$$=xa+xb$, dove $a=\frac{\sin\left(x\right)}{\cos\left(x\right)}$, $b=\frac{\cos\left(x\right)}{\sin\left(x\right)}$, $x=\cos\left(x\right)$ e $a+b=\frac{\sin\left(x\right)}{\cos\left(x\right)}+\frac{\cos\left(x\right)}{\sin\left(x\right)}$

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

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

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

Applicare la formula: $x\cdot x$$=x^2$, dove $x=\cos\left(x\right)$