Part of the utility of rational trig seems to be that it can work in any field, while functions like sin and cos only work for reals. I.e. you can use rational

Part of the utility of rational trig seems to be that it can work in any field, while functions like sin and cos only work for reals. I.e. you can use rational trig describe the "geometry" of a "triangle" whose points have coordinates in a finite field