The best way to tell is by just asking him. This might be hard, especially if he feels uncomfortable talking about it or if he actually isn't gay. You could ask your friend how he/she got the information and try to figure it out from there.
you ask your boyfriend if that is true
Tell her your a true friend and tell her the truth. Do you or do you not.
Ask him whether it is true!
definitely be true!
talk to your friend, tell her to back off. either that, or if she's hitting on your boyfriend then she isn't a true friend.
you tell the people you told, the truth
That depends on if it bothers you or not? If it does tell your friend. If she is a true friend then she'll respect your wishes and will stop seeing him.
ask him if its true and why he did he ask her and not you. either that or dump him
You can't convince him. You can tell him and your reasons for thinking he is not a good friend but ultimatly he must make up his mind.
Just be honest. Tell them the truth, and if they're your true friend then they would understand.
Your BRILLIANT friend, needs to tell her/his mother, that it was their idea. Not, yours.
well your friend is not a true friend whatever you do don't beg your boyfriend to take you back you will seem so needy and don't have a long boring talk with him it will just make matters worse talk to your friend ask her why she did what she did if that doesn't help just move on and find another bestie and a new boyfriend