How can I do that? I have no idea where the point(K,1) is? Since we haven't computed it.If you have been making a drawing of this (which you should), you can look at the triangle formed by the origin (0,0), the center of my "screen segment" (0,1) and the far right end of my screen segment (K,1).
Here is what I drew up until that point:

EDIT 2: I'm not sure if we are using cartesian-coordinate system or normal math one?
What exactly is distance_to_screen? and also your using player like a struct then telling me player is a vector representing the origin of the player?
EDIT:
On a second note maybe one thing should be clarified as well:
1. "The pixel columns on your screen don't cover a constant angle" - I'm not 100% sure I get that statement, maybe a picture ( when you have time of course! ) along with words could help straighten that out.
PS. I'm so sorry for getting this slow, and that you take a lot of time explaining it to me.

