"Le cinture sono le mie" could be correct, but it would have a slightly different nuance.
"Le cinture sono le mie." The belts are mine, probably the only ones I have, and probably somebody thought those were from somebody else.
"Le cinture sono mie" is more generic, you can always use it.
That's the clearest explanation I've had for the use or not of the article. Thanks.
when we say "... mine" its "mie" without the article and when we say "my ..." its "le mie". Is this a correct way to think about it?