program Sechenie;
{ Turbo Pascal 7.0 (DOS). Готово к копированию и компиляции. }

uses Graph;

const
  { --- Двутавр No20 (ГОСТ 8239-89) --- }
  b2 = 10.0;   h2 = 20.0;   d2 = 0.52;  t2 = 0.84;
  F2 = 26.8;   Ix2 = 1840.0; Iy2 = 104.0;

  { --- Уголок 180x110x12 (ГОСТ 8510-86) --- }
  B1 = 18.0;   b1 = 11.0;   t1 = 1.2;
  F1 = 33.69;  Ix1 = 1122.56; Iy1 = 324.09; Ix1y1 = 348.0;
  x0 = 2.52;   y0 = 5.97;

var
  gd, gm : integer;
  scale  : double;
  cx0, cy0 : integer;

  xc1, yc1, xc2, yc2 : double;
  F, xc, yc : double;
  a1, b1_, a2, b2_ : double;
  Jx, Jy, Jxy : double;
  alpha0 : double;
  Javg, Jrad, Jmax, Jmin, iu, iv : double;

{ ---------- arctan2 (в TP7 нет) ---------- }
function ArcTan2(y, x: double): double;
begin
  if x > 0 then
    ArcTan2 := ArcTan(y/x)
  else if x < 0 then
  begin
    if y >= 0 then ArcTan2 := ArcTan(y/x) + Pi
    else ArcTan2 := ArcTan(y/x) - Pi;
  end
  else
  begin
    if y > 0 then ArcTan2 := Pi/2
    else if y < 0 then ArcTan2 := -Pi/2
    else ArcTan2 := 0;
  end;
end;

{ ---------- форматирование числа в строку ---------- }
function Fmt(v: double; dec: integer): string;
var
  s : string;
begin
  Str(v:0:dec, s);
  Fmt := s;
end;

{ ---------- экранные координаты ---------- }
function SX(x: double): integer;
begin
  SX := Round(cx0 + x * scale);
end;

function SY(y: double): integer;
begin
  SY := Round(cy0 - y * scale);
end;

procedure WLine(x1,y1,x2,y2: double);
begin
  Line(SX(x1), SY(y1), SX(x2), SY(y2));
end;

{ ---------- заливка полигона (scanline) ---------- }
procedure FillPolyWorld(var xs, ys: array of double; color: word);
var
  i, j, k, n : integer;
  ymin, ymax, yy : double;
  xint : array[0..255] of double;
  cnt, xi, xj : integer;
  px1, px2 : integer;
  t : double;
begin
  n := Length(xs);
  ymin := ys[0]; ymax := ys[0];
  for i := 1 to n-1 do
  begin
    if ys[i] < ymin then ymin := ys[i];
    if ys[i] > ymax then ymax := ys[i];
  end;

  SetColor(color);
  yy := ymin;
  while yy <= ymax do
  begin
    cnt := 0;
    j := n - 1;
    for i := 0 to n-1 do
    begin
      xi := i; xj := j;
      if ((ys[xi] <= yy) and (ys[xj] > yy)) or
         ((ys[xj] <= yy) and (ys[xi] > yy)) then
      begin
        t := (yy - ys[xi]) / (ys[xj] - ys[xi]);
        xint[cnt] := xs[xi] + t * (xs[xj] - xs[xi]);
        Inc(cnt);
      end;
      j := i;
    end;
    for i := 0 to cnt-2 do
      for k := i+1 to cnt-1 do
        if xint[i] > xint[k] then
        begin
          t := xint[i]; xint[i] := xint[k]; xint[k] := t;
        end;
    i := 0;
    while i < cnt-1 do
    begin
      px1 := SX(xint[i]);
      px2 := SX(xint[i+1]);
      Line(px1, SY(yy), px2, SY(yy));
      i := i + 2;
    end;
    yy := yy + 0.05;
  end;
end;

{ ---------- повернутый эллипс ---------- }
procedure DrawEllipse(cx, cy, a, b, ang: double);
var
  t, x, y, xr, yr : double;
  n, i : integer;
  px, py, pxp, pyp : integer;
begin
  n := 360;
  t := 0;
  x := a; y := 0;
  xr := x*cos(ang) - y*sin(ang) + cx;
  yr := x*sin(ang) + y*cos(ang) + cy;
  pxp := SX(xr); pyp := SY(yr);
  for i := 1 to n do
  begin
    t := 2*Pi*i/n;
    x := a*cos(t); y := b*sin(t);
    xr := x*cos(ang) - y*sin(ang) + cx;
    yr := x*sin(ang) + y*cos(ang) + cy;
    px := SX(xr); py := SY(yr);
    Line(pxp, pyp, px, py);
    pxp := px; pyp := py;
  end;
end;

var
  i : integer;
  xs, ys : array[0..20] of double;
  L, dx, dy : double;

begin
  { --- Расчёт --- }
  xc1 := b2/2 + x0;
  yc1 := y0;
  xc2 := 0; yc2 := 0;
  F := F1 + F2;
  xc := (F1*xc1 + F2*xc2) / F;
  yc := (F1*yc1 + F2*yc2) / F;

  a1 := yc1 - yc;  b1_ := xc1 - xc;
  a2 := yc2 - yc;  b2_ := xc2 - xc;

  Jx  := Ix1 + F1*a1*a1 + Ix2 + F2*a2*a2;
  Jy  := Iy1 + F1*b1_*b1_ + Iy2 + F2*b2_*b2_;
  Jxy := Ix1y1 + F1*a1*b1_ + 0 + F2*a2*b2_;

  alpha0 := 0.5*ArcTan2(-2*Jxy, Jx-Jy);
  Javg := (Jx+Jy)/2;
  Jrad := 0.5*Sqrt(Sqr(Jx-Jy) + 4*Jxy*Jxy);
  Jmax := Javg + Jrad;
  Jmin := Javg - Jrad;
  iu := Sqrt(Jmax/F);
  iv := Sqrt(Jmin/F);

  { --- Графика --- }
  gd := Detect;
  InitGraph(gd, gm, '');
  if GraphResult <> grOk then Halt(1);

  scale := 20.0;
  cx0 := 300;
  cy0 := 400;

  { --- Сетка 1 см --- }
  SetColor(LightGray);
  SetLineStyle(DottedLn, 0, NormWidth);
  for i := -10 to 20 do
    Line(SX(i), SY(-15), SX(i), SY(25));
  for i := -15 to 25 do
    Line(SX(-10), SY(i), SX(20), SY(i));
  SetLineStyle(SolidLn, 0, NormWidth);

  { --- Оси x2, y2 --- }
  SetColor(Blue);
  WLine(-10, 0, 20, 0);
  WLine(0, -15, 0, 25);
  OutTextXY(SX(19), SY(0.5), 'x2');
  OutTextXY(SX(0.5), SY(24), 'y2');

  { --- Двутавр --- }
  xs[0] := -b2/2;  ys[0] :=  h2/2;
  xs[1] :=  b2/2;  ys[1] :=  h2/2;
  xs[2] :=  b2/2;  ys[2] :=  h2/2-t2;
  xs[3] :=  d2/2;  ys[3] :=  h2/2-t2;
  xs[4] :=  d2/2;  ys[4] := -h2/2+t2;
  xs[5] :=  b2/2;  ys[5] := -h2/2+t2;
  xs[6] :=  b2/2;  ys[6] := -h2/2;
  xs[7] := -b2/2;  ys[7] := -h2/2;
  xs[8] := -b2/2;  ys[8] := -h2/2+t2;
  xs[9] := -d2/2;  ys[9] := -h2/2+t2;
  xs[10]:= -d2/2;  ys[10]:=  h2/2-t2;
  xs[11]:= -b2/2;  ys[11]:=  h2/2-t2;
  xs[12]:= -b2/2;  ys[12]:=  h2/2;

  FillPolyWorld(xs, ys, LightBlue);
  SetColor(Black);
  for i := 0 to 11 do
    WLine(xs[i], ys[i], xs[i+1], ys[i+1]);
  WLine(xs[12], ys[12], xs[0], ys[0]);

  { --- Уголок --- }
  xs[0] := b2/2;       ys[0] := 0;
  xs[1] := b2/2;       ys[1] := B1;
  xs[2] := b2/2 + t1;  ys[2] := B1;
  xs[3] := b2/2 + t1;  ys[3] := t1;
  xs[4] := b2/2 + b1;  ys[4] := t1;
  xs[5] := b2/2 + b1;  ys[5] := 0;
  xs[6] := b2/2;       ys[6] := 0;

  FillPolyWorld(xs, ys, LightRed);
  SetColor(Black);
  for i := 0 to 5 do
    WLine(xs[i], ys[i], xs[i+1], ys[i+1]);
  WLine(xs[6], ys[6], xs[0], ys[0]);

  { --- Центральные оси --- }
  SetColor(Green);
  WLine(-10, yc, 20, yc);
  WLine(xc, -15, xc, 25);
  OutTextXY(SX(19), SY(yc+0.6), 'x');
  OutTextXY(SX(xc+0.5), SY(24), 'y');

  { --- Главные оси u, v --- }
  SetColor(Red);
  L := 20;
  dx := cos(alpha0)*L;  dy := sin(alpha0)*L;
  WLine(xc-dx, yc-dy, xc+dx, yc+dy);
  OutTextXY(SX(xc+dx*0.9), SY(yc+dy*0.9), 'u');

  SetColor(Magenta);
  dx := -sin(alpha0)*L;  dy := cos(alpha0)*L;
  WLine(xc-dx, yc-dy, xc+dx, yc+dy);
  OutTextXY(SX(xc+dx*0.9), SY(yc+dy*0.9), 'v');

  { --- Эллипс инерции --- }
  SetColor(DarkGray);
  DrawEllipse(xc, yc, iu, iv, alpha0);

  { --- Точки центров --- }
  SetColor(Green);
  SetFillStyle(SolidFill, Green);
  FillCircle(SX(xc), SY(yc), 5);
  OutTextXY(SX(xc)+8, SY(yc)-8, 'C');

  SetColor(LightRed);
  SetFillStyle(SolidFill, LightRed);
  FillCircle(SX(xc1), SY(yc1), 5);
  OutTextXY(SX(xc1)+6, SY(yc1)-8, 'C1');

  SetColor(Blue);
  SetFillStyle(SolidFill, Blue);
  FillCircle(SX(xc2), SY(yc2), 5);
  OutTextXY(SX(xc2)+6, SY(yc2)+2, 'C2');

  { --- Текст результатов --- }
  SetColor(Black);
  OutTextXY(10, 10, 'Dvutavr No20 + Ugolok 180x110x12');
  OutTextXY(10, 25, 'xc = ' + Fmt(xc,2) + ' sm,  yc = ' + Fmt(yc,2) + ' sm');
  OutTextXY(10, 40, 'Jx = ' + Fmt(Jx,1) + ',  Jy = ' + Fmt(Jy,1) + ' sm4');
  OutTextXY(10, 55, 'Jxy = ' + Fmt(Jxy,1) + ' sm4');
  OutTextXY(10, 70, 'alpha0 = ' + Fmt(alpha0*180/Pi,2) + ' grad');
  OutTextXY(10, 85, 'Ju = ' + Fmt(Jmax,1) + ',  Jv = ' + Fmt(Jmin,1) + ' sm4');
  OutTextXY(10, 100,'iu = ' + Fmt(iu,2) + ' sm,  iv = ' + Fmt(iv,2) + ' sm');

  SetColor(Blue);    OutTextXY(10, 130, '--- osi x2,y2');
  SetColor(Green);   OutTextXY(10, 145, '--- centralnye x,y');
  SetColor(Red);     OutTextXY(10, 160, '--- glavnaya u');
  SetColor(Magenta); OutTextXY(10, 175, '--- glavnaya v');
  SetColor(DarkGray);OutTextXY(10, 190, '--- ellips inercii');

  OutTextXY(10, 220, 'Nazhmite Enter dlya vyhoda...');
  ReadLn;

  CloseGraph;
end.