It's mostly leftover randomonium from Trigonometry that has to be learned to take Calculus.
The only people who wind up taking this are people who could get through Geometry in the first place (which is why there are less definitions of this than regular "Geometry").
Since math is in logical form, studies of shapes are mathematical; therefore, this fits the description and anyone who says otherwise is an idiot-of-all-trades for not recognizing that (which are a lot of the definitions of "Geometry").
Guy 2: "Well, I'll see ya in about ten months from now, when you pass it."
Guy 1: "That sounds about right".