text: var btn = document.getElementById('btn');
  var simplify = document.getElementById('simplify');
  var factor = document.getElementById('factor');
  var derive = document.getElementById('derive');
  var integrate = document.getElementById('integrate');
  var zeroes = document.getElementById('zeroes');
  var ftangent = document.getElementById('ftangent');
  var area = document.getElementById('area');
  var cos = document.getElementById('cos');
  var sin = document.getElementById('sin');
  var tan = document.getElementById('tangent');
  var cosin = document.getElementById('cosin');
  var sinin = document.getElementById('sinin');
  var tanin = document.getElementById('tanin');
  var abs = document.getElementById('abs');
  var log = document.getElementById('log');
  var operation = "";
  var expression = document.getElementById('expression');
  
  simplify.addEventListener("click", function (){
  	operation = "simplify";
  	document.getElementById('operation').insertAdjacentHTML('afterbegin', "Operation to perform: " + operation);
  });
  
  factor.addEventListener("click", function (){
  	operation = "factor";
  	document.getElementById('operation').insertAdjacentHTML('afterbegin', "Operation to perform: " + operation);
  });
  
  derive.addEventListener("click", function (){
  	operation = "derive";
  	document.getElementById('operation').insertAdjacentHTML('afterbegin', "Operation to perform: " + operation);
  });
  
  integrate.addEventListener("click", function (){
  	operation = "integrate";
  	document.getElementById('operation').insertAdjacentHTML('afterbegin', "Operation to perform: " + operation);
  });
  
  zeroes.addEventListener("click", function (){
  	operation = "zeroes";
  	document.getElementById('operation').insertAdjacentHTML('afterbegin', "Operation to perform: " + operation);
  });
  
  ftangent.addEventListener("click", function (){
  	operation = "tangent";
  	document.getElementById('operation').insertAdjacentHTML('afterbegin', "Operation to perform: " + operation);
  });
  
  area.addEventListener("click", function (){
  	operation = "area";
  	document.getElementById('operation').insertAdjacentHTML('afterbegin', "Operation to perform: " + operation);
  });
  
  cos.addEventListener("click", function (){
  	operation = "cos";
  	document.getElementById('operation').insertAdjacentHTML('afterbegin', "Operation to perform: " + operation);
  });
  
  sin.addEventListener("click", function (){
  	operation = "sin";
  	document.getElementById('operation').insertAdjacentHTML('afterbegin', "Operation to perform: " + operation);
  });
  
  tan.addEventListener("click", function (){
  	operation = "tan";
  	document.getElementById('operation').insertAdjacentHTML('afterbegin', "Operation to perform: " + operation);
  });
  
  cosin.addEventListener("click", function (){
  	operation = "arccos";
  	document.getElementById('operation').insertAdjacentHTML('afterbegin', "Operation to perform: " + operation);
  });
  
  sinin.addEventListener("click", function (){
  	operation = "arcsin";
  	document.getElementById('operation').insertAdjacentHTML('afterbegin', "Operation to perform: " + operation);
  });
  
  tanin.addEventListener("click", function (){
  	operation = "arctan";
  	document.getElementById('operation').insertAdjacentHTML('afterbegin', "Operation to perform: " + operation);
  });
  
  abs.addEventListener("click", function (){
  	operation = "abs";
  	document.getElementById('operation').insertAdjacentHTML('afterbegin', "Operation to perform: " + operation);
  });
  
  log.addEventListener("click", function (){
  	operation = "log";
  	document.getElementById('operation').insertAdjacentHTML('afterbegin', "Operation to perform: " + operation);
  });
  
  console.log(simplify);
  btn.addEventListener("click", function (){
  	expression = document.getElementById('expression').value;
  	console.log(expression);
  	var ourRequest = new XMLHttpRequest();
  	ourRequest.open('GET', 'https://newton.now.sh/' + operation + '/' + expression);
  
  	ourRequest.onload = function() {
  		var ourData = JSON.parse(ourRequest.responseText);
  		renderData(ourData);
  	};
  
  	ourRequest.send();
  });
  
  function renderData(someData){
  	var answerString = "";
  	var answer = someData.result;
  	answerString += "Answer is:<br>" + answer;
  	document.getElementById('answer').insertAdjacentHTML('afterbegin', answerString);
  } 