I studied Maths to the second highest level available in high school (so higher than the majority of students) and although I used e.g. 2PiR all the time this i

I studied Maths to the second highest level available in high school (so higher than the majority of students) and although I used e.g. 2PiR all the time this is the first I've actually understood how it works. It isn't something we were taught. We were taught how to get the answer, not why/how that is the correct way to get the answer.