High school math is often taught as simple facts, without proper explanation of the significance or how it's derived. It's entirely possible to learn how radians correspond to degrees and what you can do with them without understanding where they come from or what they mean.

I learned all the rules of logarithms in 10th grade, but didn't actually know what a logarithm was until chemistry in college. They just.. didn't really tell us. And how often are integrals explained as "the area under a curve", which is a definition that makes absolutely no sense?