Is this code correct?

Sat Apr 1 15:32:27 UTC 2023

On Friday, 31 March 2023 at 13:11:58 UTC, z wrote:
> I've tried to search before but was only able to find articles 
> for 3D triangles, and documentation for OpenGL, which i don't 
> use.

The first function you posted takes a 3D triangle as input, so I 
assumed you're working in 3D. What are you working on?

> Determines if a triangle is visible.

You haven't defined what 'visible' means for a geometric triangle.