it is worth the trouble为什么trouble前面加了the搞不懂啊,形容词后面为什么加the

be worth这个词用法比较特别的.（属于及物动词范畴）
1.be worth+vt-ing表示值得被做（v-ing是及物动词,但不加宾语的）
如：
The book is worth reading.
2.be worth+钱数
The book is worth 20 yuan.
3.be worth+n(the trouble/it/a visit)等
I am spending a lot of money and time on this boat,but it is worth it?
我正把大量的金钱和时间花在这艘船上,但这样做值得吗?
This restaurant is well worth a visit.
这家饭店很值得光顾.
Is it worth all the trouble?
那件事值得那样费神吗?
the trouble是特指前面的麻烦,所以,加the