| I'd argue it's not so much taught in the US as it is tested. The common core standards say [0] that students should: > Understand radian measure of an angle as the length of the arc on the unit circle subtended by the angle. > Explain how the unit circle in the coordinate plane enables the extension of trigonometric functions to all real numbers, interpreted as radian measures of angles traversed counterclockwise around the unit circle. and so on. However, in practice, this means that students need to be able to answer "C" when presented with the question: > One radian is: > A) Another word for degree. > B) Half the diameter. > C) The angle subtended on a unit circle by an arc of length 1. > D) Equal to the square root of 2. A surprising number of students can get through without ever really comprehending what a radian is. They might just choose the longest answer (which works way too often), identify trick answers and obviously wrong answers, and eventually guess the teacher's password from a lineup by association of the word salad of "radians" and "subtended." They might not even have a clue what the word "subtended" means, but they know it's got something to do with "radian" and that's enough. It is more important for the school that the students answer (C) than that they understand what a radian is. [0] https://web.archive.org/web/20220112000314/http://www.corest... |
This happens with very basic things like human languages. Bilingual people can forget an entire secondary language if they don’t use it for a decade+.