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