区别:
in the beginning 意为“开始时”;
at the beginning不能单独用,它后面须加of,意思为“在开始…时候”:
1、At the beginning of the meeting,he didn′t say anything;but at the end of the meeting,he said a lot.
2、In the beginning,he sang a song;but in the end,he gave a speech on how to make friends.