After reset, angular retrieves values from previous input - angularjs

Question

This is my app in Angular JS:
http://cmpe-273-010825867-fall-2016.herokuapp.com/
The problem is, when I input values into the two texts by clicking the numeric buttons, they are entered. When, i reset, the values disappear.
But when I reenter the values using the numeric buttons again, the values are appended to the values before the reset.
Here is my angular code:
var myApp = angular.module('myApp', []);
myApp.controller('myController', function($scope) {
function resetFields(){
$scope.opReset=' ';
}
function add(x, y) {
return x + y;
}
function sub(x, y) {
return x - y;
}
function mul(x, y) {
return x * y;
}
function div(x, y) {
return x / y;
}
function calc(op, x, y) {
return $scope.operators[op](parseInt(x, 10), parseInt(y));
}
$scope.operators = {
'+': add,
'-': sub,
'*': mul,
'/': div
};
$scope.op = '+';
$scope.calc = calc;
});
My HTML:
<div ng-app="myApp">
<div ng-controller="myController" ng-init='isFocused=true'>
<form>
<div class="col-lg-5 col-md-8 col-sm-12 col-xs-12">
<input width="100%" type="text" class="form-control" id="operand1" style="height:50px; font-size:32px" ng-model="operand1" ng-focus=' isFocused="operand1" ' value="{{opReset}}" autofocus>
</div>
<div class="col-lg-2 col-md-8 col-sm-12 col-xs-12 text-center" style="font-size:32px">
{{op}}
</div>
<div class="col-lg-5 col-md-8 col-sm-12 col-xs-12">
<input width="100%" type="text" class="form-control" style="height:50px; font-size:32px" ng-model="operand2" ng-focus=' isFocused="operand2" ' id="operand2" value="{{opReset}}">
</div>
<script src="js/custom.js"></script>
</div>
</div>
<div class="col-lg-5">
<div class="row">
<div class="col-lg-3 col-md-3 col-sm-12 col-xs-12 eqProps text-center">
=
</div>
<div class="col-lg-9 col-md-9 col-sm-12 col-xs-12"style="font-size:32px">
{{output}}
</div>
</div>
</div>
</div>
<div class="row">
<div class="col-lg-1"></div>
<div class="col-lg-7">
<div class="row">
<div class="col-lg-1 col-md-1 col-sm-1 col-xs-1"></div>
<div class="col-lg-10 col-md-10 col-sm-10 col-xs-10">
<div class="row-fluid">
<button class="btn btn-danger btn-fonts" type="reset" value="reset" ng-click=" opReset=resetFields() ">C</button>
<div class="btn btn-default btn-fonts" ng-repeat="n in [0]" style="margin-left:2px" ng-click='$parent[isFocused]=$parent[isFocused]+""+n' ng-disabled='isFocused===true'>{{n}}</div>
<div class="btn btn-default btn-fonts" ng-click="output=calc(op,operand1,operand2)" style="visibility:hidden">=</div>
<div class="btn btn-primary btn-fonts" ng-click="output=calc(op,operand1,operand2)">=</div>
</form>

Answer 1

Why are you using value="operand1" at all?
<input width="100%" type="text" class="form-control" id="operand1" style="height:50px; font-size:32px" ng-model="operand1" ng-focus=' isFocused="operand1" ' value="{{opReset}}" autofocus>
You can directly use ng-model to initialize the values, as well as clear it on clicking C button.
Change your text area code to remove values.
<input width="100%" type="text" class="form-control" id="operand1" style="height:50px; font-size:32px" ng-model="operand1" ng-focus=' isFocused="operand1" ' autofocus>
And then in resetFields function, change the values using:
$scope.operand1='';
$scope.operand2='';

Answer 2

please make empty value for the ng-model values(operand2,operand1)