Applicare la formula: $a=b$$\to inverse\left(a,a\right)=inverse\left(a,b\right)$, dove $a=\cos\left(a+b\right)$ e $b=-\frac{1}{2}$

Applicare la formula: $\arccos\left(\cos\left(\theta \right)\right)$$=\theta $, dove $x=a+b$

Applicare la formula: $x+a=b$$\to x=b-a$, dove $a=b$, $b=\arccos\left(-\frac{1}{2}\right)$, $x+a=b=a+b=\arccos\left(-\frac{1}{2}\right)$, $x=a$ e $x+a=a+b$