Ángulo creado por 2 segmentos 2D

function VertexAngle(x1, y1, x2, y2, x3, y3: Double): Double;
var
Dist: Double;
begin
(* Quantify coordinates *)
x1 := x1 - x2;
x3 := x3 - x2;
y1 := y1 - y2;
y3 := y3 - y2;

(* Calculate Lay Distance *)
Dist := (x1 * x1 + y1 * y1) * (x3 * x3 + y3 * y3);

if Dist = 0 then Result := 0.0
else
Result := ArcCos((x1 * x3 + y1 * y3) / sqrt(Dist)) * _180DivPI;
end;
(* End Of VertexAngle *)


Autor: Arash Partow
Homepage: http://www.partow.net