Question

to control the pitch. the trombone player uses embouchure and

Answer 1

@jigglypuff314

Answer 2

sorry for replying so late :/
I personally play the flute and don't know much about brass...
I would guess that a trombone player would change the slide length accordingly.
like slide in a little when flat
and slide out a little when sharp
like how lipping down makes it flatter
and lipping up makes it sharper