///////////////////// Draw/figures /////////////////
Ketinit();

Setketcindyjs(["Sc=1.2","Color=offwhite"]);
Setwindow([-0.5,10],[-0.5,10]);
Setscaling(0.1);
Setax(["","t","","x","","",""]);

///////////// 解曲線 ///////////////
Setscaling(1);
Slider("C",[0,-0.5],[0,10]);
inspect(C,"ptsize","5.1");
Expr(C.xy,"e2","C="+format(C.y*10,2));
Slider("K",[0,-1],[10,-1],["Size=5"]);
inspect(K,"ptsize","5.1");
Expr(K.xy,"s2","k="+format(K.x/5,2));

eq1="y'=-K.x*(y-1.5)";
eq1=Assign(eq1,["K.x",format(K.x/5,2)]);

Deqplot("1",eq1,"x=[0,XMAX]",0,C.y,["Num=200"]); 
Listplot("da1",[[0,1.5],[XMAX,1.5]],["da"]);

Htickmark([5,"5",10,"10"]);
Vtickmark([1.5,"15",5,"50",8,"80",10,"100"]);

////////////// 微分方程式の表示 /////////////
Letter([5,12],"c","ニュートンの冷却法則",["Size=1.5"]);
Expreq(eq):=(
  regional(str);
  str=eq;
  str=Assign(str,["K.x",format(K.x/5,2)]);
  str=replace(str,"y'","\frac{dx}{dt}");
  str=replace(str,"y","x");
  str=replace(str,"*","");
  str="\displaystyle "+str;
  str;
);
eq2="y'=-K.x*(y-15)";
str=Expreq(eq2);
Expr([[3,11],"e",str],["size->20"]);

Windispg();