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.
(..) - Yeah, and you? Superlative. Of course, I digress. You have my half of the triangle. And you have my father's clock. Listen, without each other we are useless at this point. We should re-evaluate our positions. You and I are in business together. We should have a business meeting. (..)2001 Lara Croft: Tomb Raider