not so ... as的用法我钢琴弹得不如我姐姐好.是I don't play the piano as well as my sister does.还是I play the piano not so well as my sister does.

not so ... as的用法我钢琴弹得不如我姐姐好.是I don't play the piano as well as my sister does.还是I play the piano not so well as my sister does.
not so ... as的用法
我钢琴弹得不如我姐姐好.是I don't play the piano as well as my sister does.还是I play the piano not so well as my sister does.

not so ... as的用法我钢琴弹得不如我姐姐好.是I don't play the piano as well as my sister does.还是I play the piano not so well as my sister does.
第二句是正确的
not so（as） …as 是不如,不像的意思
你说的这个是用在否定句中,表和谁和谁不一样；
第一句not位置用错 变成了 not…as…as并非not as…as
don’t是否定词 as…as是用在肯定句中 表示和…一样
所以第一句语法就错误了