Trigonometric Functions: Angles of Any Magnitude (2 of 2: Obtuse & reflex angles)

[guitarista]

I've taken college trig and scoured at least a half dozen trig textbooks to find even an admission that
using the coordinate plane to define trig functions greater than 90 degrees needs to be justified
mathematically. That this method works and gives accurate results is hardly obvious.

[solartypo]

actually so helpful i wish i was taught by this guy