in表示在某一范围内角落 The blooms are in the corner of the room. on表示在拐角(外面)上 The box is on the corner of the desk. at表示在拐角周围 Be careful when you are at the corner of the street.
都是拐角处的意思,但用法却不一样: in the corner:在里面的拐角处:比如说屋里面的拐角处有一张桌子 There is a table in the corner of the horse on the corner:在拐角之上。如在桌子角上放着个杯子 There is a cup on the corner of the table at he corner:在拐角外面,如问路回答:请在前面的拐角处左拐 Please turn left at the corner of the horse. 希望对你有些帮助,还有不明白我们可以再讨论,一起提高