fct = new Array(0,"f(x)+2","f(x)-2","f(x+2)","f(x-2)","2f(x)","-2f(x)","f(2x)","f(x)/2","f(x/2)","1-f(x+2)")
var fctNum=Math.floor(5*Math.random())+1;
var step = 0
var fctStep=0
var probNum
T = new Array(11)
tested=new Array(1,0,0,0,0,0,0,0,0,0,0)
order0=new Array(0,0,0,0,0,0,0,0,0,0,0)
order=new Array(0,0,0,0,0,0,0,0,0,0,0)
fctChosen=new Array(1,0,0,0,0,0)

for(var i=1;i<11;i++){
  with(Math){
    zed=floor(10*random())+1
    if(order0[zed]!=0){
      b=1        
      while (order0[b]!=0) {b++}
      order0[b]=i
    }
    else {order0[zed]=i}
  }
}
for(var i=1;i<11;i++){
  b=1
  while(order0[b]!=i){b++}
  order[i]=b
}
function checkAns(){
  if (document.answer.answers.options[order[probNum]-1].selected){
    alert("Your answer is correct!")
  }
  else {alert("Your answer is wrong. Try again.")}
}
function selectNewFunction() {
  if (fctStep < 5) {
   with(Math){    
      fctNum=floor(5*random())+1
      if (fctChosen[fctNum]) {
        b=1
        while (fctChosen[b]) {b++}
        fctNum=b
      }
      fctChosen[fctNum]=1
      fctStep++
    }
    document.answer.nextEq.value="Next graph."
  }
  if (fctStep==5) {
    document.answer.nextFct.value="Done!"
  }
  T[0] = new Image()
  T[0].src=""+fctNum+".gif"
  for(var i=1;i<11;i++){
    T[i] = new Image()
    T[i].src = ""+fctNum+"-"+i+".gif"
  }
  document.graph.src=T[0].src
  step=0
  for(var i=1;i<11;i++){
    tested[i]=0
  }   
}
function showNewGraph() {
  if (step < 10) {
    with(Math){
      probNum=floor(10*random())+1
      if (tested[probNum]) {
        b=1
        while (tested[b]) {b++}
        probNum=b
      }
      tested[probNum]=1
      step++
    }
  }
  if (step==10) {
    document.answer.nextEq.value="Done!"
  }
  document.graph1.src=T[probNum].src
}