What's the Square Root of Stupid?

I applied for a job to upgrade an antiquated legacy system to modern technology. This is in my remit and something I have done for the last twelve years as an infrastructure architect.

I expected all sorts of "How-would-you xxx?" type questions, but not like this!

Interviewer: How would you calculate a square root using java?
Me: Math.sqrt(double)

I: What if there was no square root function?
M: I would Google for John Carmack's formula to calculate it.

I: What if you could not use Google?
M: Assuming you mean no access to the internet, since I do not happen to know how to calculate a square root, I'd ask someone...

I: What if there were nobody to ask?
M: I am not a maths expert; I would go to the library and get a book on how to do it.

I: What if there were no libraries?
M: Ok, so you want me to come up with a formula I have told you I do not know, in the next 10 seconds, without access to any of the usual reference sources?


I thanked him for his time and got up to leave when the interviewer said "we're not through".

I pointed out that he knew nothing of my skills, but I now knew everything I needed to know about him, that he had failed the interview, that he had wasted enough of my time, and left.