var TraceTo[3];
...
TraceTo.x = 0;
TraceTo.y = 10000;
TraceTo.z = 0;
vec_rotate(TraceTo, my.pan);
trace_mode = ?;
c_trace(my.x, TraceTo, trace_mode;



This will trace 10,000 quants to the right of the player, ralatively. Replace all the tricky trig with a simple vec_rotate();