Ketinit();

Setketcindyjs(["Sc=1","Label=[]","Color=offwhite"]);
Ketcindyjsmain(["<pf10/fp>_;_;2次曲線の変形"],[
 "<pf5/fpbr>_;離心率$e$を変えると，楕円，放物線，双曲線が現れる．"
]);

Seteditable(30,["","Size=18","Width=50"]);

//import("Graph1.txt");
////////// 入力窓の設定 //////////
str0="0.8"; //no ketjs
//str0=Textedit(30); //only ketjs

////////// xy座標の設定 //////////
Setwindow([-10,10],[-10,10]);
Addax(0);
Drwxy();

Htickmark([XMIN,text(XMIN),XMAX,text(XMAX)]);
Vtickmark([YMIN,text(YMIN),YMAX,text(YMAX)]);

////////// 問題文の設定 //////////
Letter([2,10],"e","離心率$e=$",["Size=1.2"]);
Expr([8,10],"e","(>0)",["Size=1.2"]);

////////// グラフの設定 //////////
blue="Color=blue";
red="Color=red";
Pointdata("f1",[4,0],["Size=5",blue]);
Pointdata("f2",[-4,0],["Size=5",blue]);
F1=ptf1_1; F2=ptf2_1;
Expr([F1,"n","\mathrm{F}",F2,"n","\mathrm{F}'"],["Size=1.2"]);
Listplot("1",[[0,YMIN],[0,YMAX]],[blue]);
Expr([0,YMIN],"s","\ell",["Size=1.2"]);
e=parse(str0); Defvar("e",e);
Implicitplot("1","sqrt((x-4)^2+y^2)="+str0+"*x","x=[XMIN,XMAX]","y=[YMIN,YMAX]",["dr,1.5","Num=200"]);
y0=4*e; Defvar(["y0",y0]);
Pointdata("p1",[4,y0],["Size=5"]);
P1=ptp1_1;
Letter(P1,"nw","P$(x,y)$");
Pointdata("h",[0,y0],["Size=5",blue]);
H=pth_1;
Letter(H,"nw","H");
Listplot("b1",[F1,P1,H],[blue]);
Listplot("para1",[H+[0,-0.5],H+[0.5,-0.5],H+[0.5,0]],[blue]);
Expr([(P1+H)/2,"n","1",(F1+P1)/2,"e","e"],[blue]);
if((parse(str0)>0.6)&(parse(str0)<1),
  Letter([10,8],"n","楕円",["Size=1.2",red]);
);
if(parse(str0)==1,
  Letter([10,8],"n","放物線",["Size=1.2",red]);
);
if(parse(str0)>1,
  Implicitplot("2","-sqrt((x+4)^2+y^2)="+str0+"*x","x=[XMIN,XMAX]","y=[YMIN,YMAX]",["dr,1.5","Num=200"]);
  Pointdata("p2",[-4,y0],["Size=5"]);
  P2=ptp2_1;
  Listplot("b2",[F2,P2,H],[blue]);
);
Htickmark([-4,"-4",4,"4"]);

Windispg();