My grammar books sometimes says the reason for using "in order to(so as to)" instead of "to~" is
to clarify a purpose, and sometimes it's a formal usage. Which is correct?
1. He went to Beijing to learn Chinese.
2. He went to Beijing in order to(so as to) learn Chinese.
I don't see that in order to is more formal than to. I do use it when writing to non-native speakers when I think it will make things clearer, though.