Помогите решить умоляю

Решите задачу:

$\frac{sin(\alpha+\beta)-sin(\alpha-\beta)}{sin(\alpha+\beta)+sin(\alpha-\beta)} = \frac{sin\alpha*cos\beta+sin\beta*cos\alpha-(sin\alpha*cos\beta-sin\beta*cos\alpha)}{sin\alpha*cos\beta+sin\beta*cos\alpha+sin\alpha*cos\beta-sin\beta*cos\alpha} =\\= \frac{2sin\beta*cos\alpha}{2sin\alpha*cos\beta} = \frac{sin\beta}{cos\beta} * \frac{cos\alpha}{sin\alpha} =tg\beta*ctg\alpha=ctg\alpha*tg\beta$