What are multivariate differential equations? Is that another name for partial differential equations? If so, then I assume your office mate was joking?
Oops, I meant multivariate calculus. But he really was that far out of touch. Not to be too tough on him, he was a grad student teaching assistant with a pure math background.
That's a poor reflection on his education then. Even the purest mathematics majors I knew still were aware of the applications of most of what they learnt.
