program MeanAngle;
{$IFDEF DELPHI}
  {$APPTYPE CONSOLE}
{$ENDIF}
uses
  math;// sincos and atan2
type
  tAngles = array of double;

function MeanAngle(const a:tAngles;cnt:longInt):double;
// calculates mean angle.
// returns 0.0 if direction is not sure.
const
  eps = 1e-10;

var
  i : LongInt;
  s,c,
  Sumsin,SumCos : extended;
begin
  IF cnt = 0 then
  Begin
    MeanAngle := 0.0;
    EXIT;
  end;

  SumSin:= 0;
  SumCos:= 0;
  For i := Cnt-1 downto 0 do
  Begin
    sincos(DegToRad(a[i]),s,c);
    Sumsin := sumSin+s;
    SumCos := sumCos+c;
  end;
  s := SumSin/cnt;
  c := sumCos/cnt;
  IF c > eps then
    MeanAngle := RadToDeg(arctan2(s,c))
  else
    // Not meaningful
    MeanAngle := 0.0;
end;

Procedure OutMeanAngle(const a:tAngles;cnt:longInt);
var
  i : longInt;
Begin
  IF cnt > 0 then
  Begin
    write('The mean angle of [');
    For i := 0 to Cnt-2 do
      write(a[i]:0:2,',');
    write(a[Cnt-1]:0:2,'] => ');
    writeln(MeanAngle(a,cnt):0:16);
  end;
end;

var
  a:tAngles;
Begin
  setlength(a,4);

  a[0] := 350;a[1] := 10;
  OutMeanAngle(a,2);
  a[0] := 90;a[1] := 180;a[2] := 270;a[3] := 360;
  OutMeanAngle(a,4);
  a[0] := 10;a[1] := 20;a[2] := 30;
  OutMeanAngle(a,3);

  setlength(a,0);
end.