Angularjs ngnonbindable tutorial

<!DOCTYPE html>
<html>
   <head>
   <title>Wikitechy AngularJS Tutorial</title>
   <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.5.6/angular.min.js"></script>
   </head>
   <body>
   <div ng-app="" ng-init="text='Welcome to wikitechy'">
   <h3>ng-non-bindable Directive in AngularJS Tutorial</h3>
   <p> {{text}} </p>
   <p ng-non-bindable> {{text}} </p>
   <p>AngularJS compile this Expression: {{ 20+50 }}</p>
   <p ng-non-bindable>AngularJS Cannot compile this Expression: {{ 20+50 }}</p>
   </div>
   </body>
</html>