in的本意是指在一个范围或者在一个封闭的空间,与德文与荷兰文的介系词in是同源的,所以in the corner of指的是在某一范围内的角落,强调在直角的内角里面.用介系词in的例句有：
in a car（如果用介系词by时,冠词a就要省略,也就是by car）
I live in the USA.
The light in the window went out.（灯是在橱窗里面,用in）
I couldn't bear to see my reflection in the mirror.（虚像是成在平面镜的里面,所以也用in）
He was a big man,smartly dressed in a suit and tie.
His legs were covered in mosquito bites.（腿是被蚊子块包裹在其中,所以用in）
There was a deep crack in the ceiling above him.（这里的in表示裂缝占去天花板的一部分）
on的本意是一个平面,支撑在其表面上,on the corner of指的是在拐角上 ,强调在直角的顶点上.用介系词on的句子有：
The author's name is on the cover of the book.
I admired the peeling paint on the ceiling.
She flung the invitation on the table.
He continued to lie on his back and look at clouds.
He leaned down and kissed her lightly on the mouth.
The maid looked at him,a nervous smile on her face.
I didn't have any money on me.
Everyone's eyes were fixed on him.
Mr Pendle hit his head on a wall as he fell.
He was able to spend only a few days at a time on the island.
Bergdorf Goodman has opened a men's store on Fifth Avenue.
The writing on the back of the card was cramped but scrupulously neat.
We waited till twelve and we finally got on the plane.
Claire and Beryl were on the organizing committee.
at的本意是在一个点上,at the corner of指在拐角周围.用介系词at的句子有：
We had dinner at a restaurant in Attleborough.
My son was at school yesterday.
An assistant sat typing away at a table beside him.
The two journalists followed at a discreet distance.
He looked at Michael and laughed.
She opened the door and stood there,frowning at me.
He pointed at the empty bottle and the waitress quickly replaced it.
She lowered the handkerchief which she had kept dabbing at her eyes.
希望我能帮助你解疑释惑.