定语从句中的AS是怎么用的？

6.由as, such...as, the same...as等引出定语从句。

I shall use the instrument in such a way as he used it yesterday. 我将按他昨天使用(该仪器)的方法来使用该仪器。

Each atom normally has the same number of electrons revolving about the nucleus as it has protons in the nucleus. 通常每个原子内绕原子核旋转的电子数和原子核内的质子数相同。

As is reported in today's newspaper, the two countries have signed the treaty of peace and friendship. 据今天报纸报导，这两个国家已签署了和平友好条约。

注意：单个as引出非限制性定语从句时，as在从句中作成分，本身代替主句整个意思，翻译时，一般可译为"正如……那样" 。同时，这种as从句的位置比较灵活，既可置于句首或句末，也可插到句中；若插到句中，要用逗号将其与主句隔开。

一．若先行词是个句子,引导词用as.例如：He is a good teacher,as is known.
二．As+adj.／adv.+as+定语从句,注意：其修饰语如twice,three time one-third等放在该结构的最前面.
三.as+形容词+a/an+名词+as，例：Beijing is as large a city as London.

在限定性定语从句中经常和SUCH ,THE SMAE, AS ,SO连用
在非限定性定语从句中放在句首

用法太多了,还可以当THOUGH用,当BECAUSE,当WHEN.
Young as he is, he can speak many languages.(though)
He cannot go to school as he is too young(because)
太多了,一时半会儿说不清楚,大家都来说说看吧.