will not start

my 02 gp gt will not start. tried to start but only a single click when turned. radio and lights turn on fine. but when locking the doors the horn sounds dead so i tried to jump it. after a few minutes still nothing. I know how to fix the car I'm just bad a diagnosing problems so any help would be appreciated.

Sounds like either corrosion on the battery terminals, bad battery or bad starter. I would suspect the battery has gone bad that is why the car won't jump start. Also if the horn sounds low the battery is probably the issue.