I'd like to know which preposition to use in the following:
We were disappointed in/at the fact that no one is interested in our products.
I'd like to know which preposition to use in the following:
We were disappointed in/at the fact that no one is interested in our products.
I think for you to sound more grammatical, you can choose another word to use like "by". But if you want to choose between the two,pick "at"
Disappointed is tricky: it can occur with any of several prepositions before the source of disappointment. Roughly:
But these differences are subtle and probably not consistent across speakers. E.g., searching the web you can find plenty of restaurant reviews with "disappointed in/at/by/with the meal".
More discussion here.
The second one is correct. "At" is used to show the cause of something with adjective.