Does a cop have to answer YES to "are you a cop"?

Depends on the juridiction that they operate in.  Often times a cop who is conducting a vice investigation will not answer or will answer no.

don't believe me...  All you have to do is tune into a COPS re-run when they are conducting a sting operation.

Maybe the better indicator would be the price....  So often on the show the UC-LE is discussing sex acts that normally are five and six times more expensive than they offer.

My advice is that if sex acts are being specifically discussed/negotiated before your and her clothes are off; then get out of there!

This is an Urban Legend!!! A provider asking someone if they are a cop DOES NOT get legal protection if they say yes or no.  The law provides certain allowances for a cop to maintain their cover when working undercover, and allows them to deny their status as LE.

Check this out for the truth...

http://www.snopes.com/risque/hookers/cop.htm

Cops can answer "no"; that's why it's called "undercover".

Do you think when the DEA cops are heavy undercover, sporting beards and tatoos and using the lingo and some meth dealer asks if he's one, he's going to say "why yes, I'm a cop".  

Think about it.

If an escort is for real they will do this.  Female LE probably would not stoop to this level for an arrest.

they dont have to deny it, during the course of an investigation, they are allowed to do whatever it takes to get the evidence they need to convict...

doing drugs with a dealer to prove they arent a narc went out the reality window in the early 80s...
same with having sex with a provider.
see everyone, collect the info, come back for the big bust.

i mean, that what the cops i'm used to do... maybe i just have 'worked under' smarter/shiftier chiefs of police than the rest of the country? (new orleans)