//ketlib
Auxflg=0;

Initglist();

aa=1.8; bb=2;
fun=Assign("x^2/a^2-y^2/b^2-1",["a",aa,"b",bb]);
Implicitplot("1",fun,"x=[-5,5]","y=[-5,5]");

Setglist();

//figures
Ketinit();
Addglist();

Setketcindyjs(["Nolabel=all"]);//no ketjs
Setwindow([-5,5],[-5,5]);
A.y=0;
Slider("T",[-5,-6],[5,-6]);

cmdL=[ //no ketjs on
 "line:[x0+u1*t,y0+v1*t]",[],
 "f:x^2/a^2-y^2/b^2-1",[],
 "fl:ev(f,[x=line[1],y=line[2]])",[],
 "ans:solve(fl=0,t)",[],
 "t1:ev(t,ans[1])",[],
 "t2:ev(t,ans[2])",[],
 "d:[diff(f,x),diff(f,y)]",[],
 "d:ev(-d,[x=x1,y=y1])",[],
 "eq1:d[1]*u1+d[2]*v1=d[1]*u2+d[2]*v2",[],
 "eq2:u2^2+v2^2=u1^2+v1^2",[],
 "res:solve([eq1,eq2],[u2,v2])",[],
 "u2:ev(u2,res[2])",[],
 "v2:ev(v2,res[2])",[],
 "x1:line[1]",[],
 "y1:line[2]",[],
 "t0:t2",[],
 "t0::x1::y1::u2::v2",[]
];
CalcbyM("ans",cmdL,[""]);
if(1==0,
 Mxtex("1",ans_1,["Disp=n"]);
 Expr([-5,4],"e",tx1,["Size=1.5"]);
 Mxtex("2",ans_2,["Disp=n"]);
 Expr([-5,2],"e",tx2,["Size=1.5"]);
 Mxtex("3",ans_5,["Disp=n"]);
 Expr([-5,0],"e",tx3,["Size=1.5"]);
 Mxtex("4",ans_6,["Disp=n"]);
 Expr([-5,-2],"e",tx4,["Size=1.5"]);
); //no ketjs off

Ketcindyjsdata(["ans",ans]);//no ketjs

Addax(0);

pF=[-sqrt(aa^2+bb^2),0];
C.xy=pF;

//Drwfigs("1",["imp1"],["Color=red"]); //

Drwxy();
Ketcindyjsdata(["imp1",imp1]);// no ketjs off

Pointdata("1",C,["Size=3","Color=red","border->false"]);
uctr=[0,0];
Circledata("1",[uctr,1],[]);
Putoncurve("B","cr1");
Arrowdata("1",[A,B],["dr,2","Color=red","border->false"]);
Putoncurve("B","cr1");
Strictmove(B);
Listplot("0",[uctr,Ptpos(B)],["dr,2","Color=red"]);
pB2=Ptpos(A)+Ptpos(B)-uctr;
Arrowdata("1",[Ptpos(A),pB2],["dr,2","Color=red","border->false"]);

Getvalue(n,rep):=(
  regional(tmp);
  tmp=Assign(ans_n,rep);
  parse(tmp);
);

mf(tt):=(
 regional(Eps,pL,ctr,tr,t1,x0,y0,x1,y1,vec,u1,v1,
   rep0,rep,rep2,flg,tmp);
 Eps=10^(-6);
 x0=Ptpos(A)_1; y0=0;
 vec=pB2-Ptpos(A);
 u1=vec_1; v1=vec_2;
 pL=[[x0,y0]];
 rep0=["a",aa,"b",bb];
 ctr=1;
 flg=0;
 tr=tt;
 while((tr>0)&(ctr<20),
   rep=concat(rep0,["x0",x0,"y0",y0,"u1",u1,"v1",v1]);
   t1=Getvalue(1,rep);
   if(t1>0,
     rep2=concat(rep,["t",t1]);
     x1=Getvalue(2,rep2);
     y1=Getvalue(3,rep2);
     rep2=concat(rep2,["x1",x1,"y1",y1]);
     u2=-Getvalue(4,rep);
     v2=-Getvalue(5,rep);
     tr=tr-t1;
     if(tr>0,
       pL=append(pL,[x1,y1]);
       x0=x1; y0=y1;
       u1=u2; v1=v2;
     );
     ctr=ctr+1;
   ,
     t1=0;
     ctr=10000;
   );
 );
 tr=tr+t1;
 if(tr>0,
   if(flg==0,
     pL=append(pL,[x0+u1*tr,y0+v1*tr]);
     flg=1;
   ,
     pL_(length(pL))=[x0+u1*tr,y0+v1*tr];
   );
 );
 if(length(pL)>1,
   Listplot("1",pL);
 );
 if(Auxflg==1,
   Listplot("2",[C.xy,[x1,y1]],["da","Color=blue"]);
 );

);

//tt=2*(T.x+5);
tt=Animationparam(0,4,20);
mf(tt);

Windispg();