Rotate a 2D Point

Rotate a 2D Point

const
  PIDiv180 = 0.017453292519943295769236907684886;

procedure Rotate(RotAng: Double; x, y: Double; var Nx, Ny: Double);
var
  SinVal: Double;
  CosVal: Double;
begin
  RotAng := RotAng * PIDiv180;
  SinVal := Sin(RotAng);
  CosVal := Cos(RotAng);
  Nx := x * CosVal - y * SinVal;
  Ny := y * CosVal + x * SinVal;
end;

Rotate a 2D Point around another 2D Point

const
  PIDiv180 = 0.017453292519943295769236907684886;

procedure Rotate2(RotAng: Double; x, y, ox, oy: Double; var Nx, Ny: Double);
begin
  Rotate(RotAng, x - ox, y - oy, Nx, Ny);
  Nx := Nx + ox;
  Ny := Ny + oy;
end;