What is the definition of Expertise Math?

"Expertise math" is like when a mathematician becomes so engrossed in numbers that they start to see patterns where there aren't any, essentially turning their brain into a super calculator that also writes poetry about pi. Now, here's an example sentence that's as unsettling as a bad math test: "After solving the problem of pi, John became so obsessed with it he started charging clients to calculate their life insurance premiums based on their favorite mathematical theorems."