I am adding a sink in a bathroom about 10 feet from the bath tub and will be tapping into the bath tub drain line. Since the sink drain is a standard hight above the floor and the drain is below the floor, do I need a dedicated vent for the new sink? Thanks.

Use a studor vent in the cabinet for the sink.

I am adding a sink in a bathroom about 10 feet from the bath tub and will be tapping into the bath tub drain line. Since the sink drain is a standard hight above the floor and the drain is below the floor, do I need a dedicated vent for the new sink? Thanks.
EVERY fixture that has a trap HAS to be vented. You may vent the sink in one of 3 ways. 1) You may run the vent out the roof. 2) You may revent back to a dry vent **or** 3) you may take Dougs advice and install a AAV(air admittance vent) just after the trap. Good luck, Tom