Ketinit();

Setketcindyjs(["Label=[X]","Color=offwhite"]);
Ketcindyjsmain(["<pf10/fp>_;_;微分係数の定義(1)"],["<pf5/fp>関数の式と$a$の値を代入して，平均変化率が微分係数に近づく様子を確認する．"]);
Seteditable(50,["y=","Size=18","Width=100"]);
Movetojs(Text50,[-1.5,4.5],18); //only ketjs
Seteditable(51,["a=","Size=18","Width=50"]);
Movetojs(Text51,[4.5,4.5],18); //only ketjs

Setwindow([-1,4],[-1,4]);

str0="y=x^2";
//str0=Textedit(50); //only ketjs
Deffun("f(x)",["regional(y)",str0,"y"]);
tmp0=Strsplit(str0,"=");
if(length(tmp0_2)>0,
  Plotdata("1",tmp0_2,"x",["dr,1.5"]);
);

str1="a=1";
//str1=Textedit(51); //only ketjs
tmp1=Strsplit(str1,"=");
if(length(tmp1_2)>0,
  aa=parse(tmp1_2);
  Pointdata("1",[aa,f(aa)],["Size=2"]);
  Listplot("1",[[aa,0],pt1_1],["do"]);
  Htickmark([aa,"a"]);
);

if((length(tmp0_2)>0)&(length(tmp1_2)>0),
  Slider("X",[XMIN,-1.5],[XMAX,-1.5]);
  Pointdata("s1",[aa,-1.5],["Size=2"]);
  Expr(pts1_1,"n1","a");
  xx=X.x;
  eps=10^(-2);
  mm=Derivative(gr1,"x="+text(aa));
  Expr([4.25,2.5],"ne","f'(a)="+text(mm),["Color=blue"]);

  if(abs(xx-aa)>eps,
    Pointdata("2",[xx,f(xx)],["Size=2"]);
    Listplot("2",[[xx,0],pt2_1],["do"]);
    Htickmark([xx,"x"]);
    Lineplot("1",[pt1_1,pt2_1]);
    Expr([4.25,3.5],"ne","x-a="+text(xx-aa));
    Expr([4.25,3],"ne","\dfrac{f(x)-f(a)}{x-a}="+text((f(xx)-f(aa))/(xx-aa)));
  ,
    Plotdata("2",text(mm)+"*(x-"+text(aa)+")+"+text(f(aa)),"x",["Color=blue"]);
    Expr([4.25,3.5],"ne","x-a=0");
  );

);

Windispg();