function AngleDegrees(pt1, pt2: TPoint): Extended;
begin
  if (pt2.X = pt1.X) then
  begin
    if (pt2.Y > pt1.Y) then
      Result := 90.0
    else
      Result := 270.0;
  end else
    Result := (ArcTan2((pt2.Y - pt1.Y), (pt2.X - pt1.X)) * (180.0 / Pi));
  if (Result < 0) then
    Result := (Result + 360.0);
end;

function AngleDegrees2(pt1, pt2: TPoint): Extended;
begin
  Result := (ArcTan2((pt2.Y - pt1.Y), (pt2.X - pt1.X)) * (180.0 / Pi));
end;

function AngleRadians(pt1, pt2: TPoint): Extended;
begin
  Result := FixR(ArcTan2((pt2.Y - pt1.Y), (pt2.X - pt1.X)));
end;

function Angle(pt1, pt2: TPoint): Extended;
begin
  Result := ((ArcTan2((pt2.Y - pt1.Y), (pt2.X - pt1.X)) * (180.0 / Pi)) + 90.0);
  if (Result < 0.0) then
    Result := (Result + 360.0);
end;

function DegreesToCompass(dgrs: Extended): Extended;
begin
  Result := FixD(dgrs + 90.0);
end;

function CompassToDegrees(cmps: Extended): Extended;
begin
  Result := FixD(cmps - 90.0);
end;

function RadiansToCompass(rdns: Extended): Extended;
begin
  Result := FixD(Degrees(rdns) + 90.0);
end;

function CompassToRadians(cmps: Extended): Extended;
begin
  Result := FixR(Radians(cmps - 90.0));
end;

var
  a, b: TPoint;

begin
  ClearDebug;
  a := Point(10, 10);
  b := Point(20, 00);
  WriteLn(Angle(a, b));
  WriteLn(AngleDegrees(a, b));
  WriteLn(Degrees(CompassToRadians(DegreesToCompass(AngleDegrees2(a, b)))));
  WriteLn((Degrees(AngleRadians(a, b))));
end.