According to this [link](https://owl.english.purdue.edu/owl/resource/540/01/) and this [one](http://www.edufind.com/english-grammar/definite-article/), in adjective/relative clause we should use **the** before the noun we are defining, that is because for example in the sentence below,

> 
> I was happy to see the policeman who saved my cat.
> 
> 
> 

even if we don't know the policeman's name, it's still a particular policeman because it is the one who saved the cat.

Whereas i found a sentence which contains adjective clause but didn't use **the**:

> 
> A woman who fell 10 meters from High Peak was lifted to safety by a
>  helicopter.
> 
> 
> 

My first question: why doesn't above sentence use **the** even though it is using an adjective clause?

My second question: in the sentence below,

> 
> The books that have red covers are new.
> 
> 
> 

Do we use **the** because of mentioning **that have red covers** or because we are talking about some specific books, for example the books on the table?

I mean do you agree with the order below for the last sentence?

First we have **The books**, so we are talking about some specific books (e.g. on the table) ,Then we restrict those books to the ones **that have red covers** and at last we add some more information about them(**are new**).