"Compatibility Triggerfish are usually fairly aggressive so care should be taken when choosing tank mates. Suitably sized eels, groupers, snappers, squirrelfish, tangs, and wrasses would all be good choices. Invertebrates are probably best left out of the triggerfish aquarium, as they might become a meal."
be sure to add the tang first, as they are usually less dominate in these types of tanks. Also note that an proper sized tank is needed as well, because with fish, results do vary.
I would put the tang and trigger together...Introduce tang first also make sure your tank is the appropriate size for these two fish the bigger the tank the less hostility between the two....And the flame angel and trigger your asking for it... lol