Applicare la formula: $\frac{a}{b}\frac{c}{f}$$=\frac{ac}{bf}$, dove $a=x$, $b=2$, $c=\sin\left(x\right)$, $a/b=\frac{x}{2}$, $f=1-\cos\left(x\right)$, $c/f=\frac{\sin\left(x\right)}{1-\cos\left(x\right)}$ e $a/bc/f=\frac{x}{2}\frac{\sin\left(x\right)}{1-\cos\left(x\right)}$