>>11515943I picked an outer vertex to start with. Then I formed a line by connecting it with an adjacent vertex. I counted the number of vertices that would form a triangle with the line I made. Then, I made a new line by connecting my original vertex with the next outer vertex (clockwise). I counted the number of valid vertices again, excluding the vertex I had counted for previously. Doing this for each vertex, you can make 6, 3, 2, and 3 triangles (respectively), plus the last triangle (made by connecting outer vertex with two inner ones that hadn't been counted yet). From this, I knew that repeating the same counting procedure starting with the next (clockwise) outer vertex would yield the same result, but I would overcount by the number of triangles formed by the line between this vertex and my original vertex, so I would need to subtract 6. For the next vertex, I'd need to subtract 6+3, for the next 6+3+2, and so on. Add up all the triangles and you get 35. There's probably a better way to do this though
