bisector:=proc(a,b,c,d)
	local x, y, # x-y expresions of param rep
		mx, my,
		run, rise;
	mx := (a+c)/2;
	my := (b+d)/2;
	run := -(d-b);
	rise := (c-a);
	x := mx + t * run;
	y := my + t * rise;
	RETURN([x,y]);
end; # bisector

inter := proc(L1, L2)
	local	subsL2, eq1, eq2, sol;
	subsL2 := subs(t=s, L2);
	eq1 := op(1, L1) - op(1, subsL2);
	eq2 := op(2, L1) - op(2, subsL2);
	sol := solve({eq1, eq2}, {s, t});
	RETURN(subs(sol, L1));	
end; # inter