It's 'useless' trying to change her mind. = It's 'useless' to try to change her mind.
Drugs are 'useless' in treating the condition.
I made a 'useless' attempt at fixing the leak.
(..) - What? You gotta gimme something here, cause this is redonkulous. Absolutely redonkulous! Capisch redonkulous! Ya know what that means? You pigeons are useless. I need someone on the inside, someone close to the green-eyed man. - A cat. - Oh, a cat? Yeah, a cat. When I find him... (..)2008 Bolt