At the corner or in the corner?

Furniture goes "in" corners, so you are correct. The book is wrong.

In enclosed or well-defined spaces, such as rooms (but also a garden for instance), things are placed *in* corners. If the corner is a street corner, where a person is being picked up or dropped off, or a business is located, we would say it is *at* the corner or *on* the corner.

In this case*

In the corner is correct.

In the corner is correct. Because you are *in* the room, the chair is in the corner. You use *in* for the corner of an enclosed space. If you tell me something is *at* the corner of the room, I would understand. It’s imprecise but it’s not an error. At the corner is grammatically fine and it even carries the right meaning; it’s just not the word we would use because a more precise word is available.

I can see why they had at; if you were explaining the bedroom in the past tense, you would say the chair was at that corner. If you rearranged the sentence to say, a chair is in the corner, that’s present tense. I know English is weird as heck to learn, but because they used the past tense “was,”they wanted the past tense “at. I will add that most people will use in the corner, but that’s because there is a lot of familiar phrases used in certain areas.

“At the corner” is the most straightforward wording because it describes the relationship between the chair and corner the simplest way possible. “At” describes the corner as nothing but a location, whereas “in” creates an additional meaning that it possesses confines within which something can be.

I don't think that "at the corner" is incorrect but "in the corner" is definitely more conventional in modern English.

"At/on the corner" usually refers to the street corner, where the mothers of all the people I play WoW with work. It is the corner of the block. Geographical location. "The Starbucks is at/on the corner of 4th and Main." For referring to putting something somewhere where there happens to be a corner, it is going in the corner. Slightly less specific, wouldn't be found on a map. "In the far corner of the yard," "in the corner by the window," etc.

Both "at" and "in" can be used with "corner", but the context changes. AT the corner is somewhere that two people, things, or ideas can meet. For instance, *meet me AT the corner of Main Street and Broadway* \- two streets have an intersection, slang is "corner" for this. *AT the corner of dreams and financing* \-- an abstract idea that helps people find funding to start their business, go to college, open an art studio, etc. You need both a dream AND money, you can't succeed without some of both. (If not money, then some other resource, like space or materials). . . IN the corner is a location or concept of being out of the way, or maybe stuck or trapped. Where is the dog's food? It is over there, out of the way *in the corner* of the room. I didn't want to talk to anyone, but my friend was still enjoying the party, so I went and sat in the corner so I could wait for them quietly.

"in the corner " will be the right option

Corner is an odd word because it means two opposite things. Mind you so does cleave.

At emphasize the point you place the things, while In emphasize the space you place the things. That’s my understanding this two when connected to place.

at this point, we should rename the sub "correcting bad English learning material."

Some languages (like Spanish) differentiate between an inside corner (you use in) and an outside corner (you use at).

That would be my interpretation, yes. “In” is certainly more commonly used in such cases.