imgran wrote:You really don't need to get too exotic to figure out a reason why that would happen.
It's far less likely to be insidious magical influence from the summoning spell as it is to be simple use-it-or-lose it.
Sorry, losing the ability due to time-lapse memory loss is not the same as forgetting the function. You may forget a lot of trig from school, but 80 years later when you die of old age, you'll still remember the purpose of trig and what the name means. And even if you forget the formulas. Remembering the function means you could reverse engineer the formulas given some time and patience, and a lot of scratch paper.
I took a college entrance exam last week after not seeing a math class since 1988. But since the test was un-timed I sat there and reverse engineered the Pythagorean theorem in order to solve a word problem. I couldn't remember the theorem but since I had spent some effort understanding why the theorem worked, it wasn't that hard to re-build the equation. That 20 question test took me about 4 hours to finish but my score was worth the effort.