HTML | Code | AngularJS - Using Expressions

HTML:
<div  ng-app="mainApp" ng-init="quantity=10;cost=40;firstName='Sam';lastName='Anderson';student={firstName:'Nick',lastName:'Anderson'};exArray=[10,15,20,30,40,50]" ng-controller="MainCtrl">
        <h4>Expression using constants : {{ 50 + 50 }}</h4>        
        <h4>Expression using controller variables: {{helloWorldString}}</h4>        
        <h4>Expression using global variables (Using Currly Binding) : {{ quantity * cost }}</h4>
        <h4>Expression using global variables (Using ng-bind): <span ng-bind="quantity * cost"></span></h4>
        <h4>Expression using global variables - String operation: <span ng-bind="firstName + ' ' + lastName"></h4>
        <h4>Expression using global variables - Object operation: <span ng-bind="student.lastName"></h4>
        <h4>Expression using global variables - Array operation: <span ng-bind="exArray[3]"></h4>
    </div>