No need to announce anything. Just play your game. Force him to resign by playing your moves and not by your wisdom.
Yeah a few reasons:
1. I'm not sure talking is allowed other than draw offers or resignations.
2. It's a little offensive 'I've seen more than you'. Maybe you don't care for offending people but maybe they wont analyse with you.
3. You may be wrong in which case you look stupid.
Just play moves.
Yeah I always thought it seemed cool when players announce mate in movies/TV, but I figured it was probably rude to do it in real life.
zip it clowns
Abdallahkh, you sound ten years old.
zip it clown