Translation:Teacher Li is not happy today.
I think there is a subtle differences between 高兴 and 开心. I read in another post (maybe where kaixin was introduced) that bugaoxing and bukaixin can be two different kind of unhappy.
Not sure which is which, but one could mean depressed and another angry. Can anyone clarify it, please?
To an untrained ear (including myself) it does sound the same even if a native speaker were to say it to you face to face. What might help is that even though the consonants (the j in jin and t in tin) might sound similar, in Chinese they often say a slight h after the t's like in "tian" ["t(h)ian"]. So, even if "tin" were an actual word in Chinese, you'd know the difference because it would be pronounced "t(h)in" but "jin" is still "jin." Take jian1 间 and tian1 天, they'd sound pretty identical if not for the "h" in "tian"'s pronunciation.
In British English as spoken in Royal Navy circles “not pleased”, without any reason given for not being pleased, means the same as “not happy”. So you could say “How is the commander today?“ “He’s not pleased“. “About what?“ “Nothing in particular – he’s just not pleased“. But it’s an uncommon use in English I suggest.