To utilize the mainapp properly, it needs to be declared as an angular module in your JavaScript code that is included in the index.html file.
Upon the document ready event triggering, Angular scans the DOM for elements with the ng-app attribute. It then proceeds to initialize the first one it encounters by executing any .config blocks, followed by any .run blocks. If there is a router set up, it will determine the appropriate templates and controllers based on the URL after resolving any asynchronous tasks (if specified). In this scenario, it seems like the failure might be due to not defining the module correctly or at all.
angular.module('mainapp',[])
<html>
<head>
<script src="http://ajax.googleapis.com/ajax/libs/angularjs/1.4.8/angular.min.js"></script>
</head>
<body ng-app="mainapp">
<div id="slidingDiv">
<section id="Proposal">
<div class="container cev2">
<div class="grid-1 ev">
<h1>Contact Information</h1>
<form class="form-horizontal" role="form">
<div class="form-group">
<label class="control-label col-sm-2" for="name">Name:</label>
<div class="col-sm-10">
<input type="name" class="form-control" id="name" placeholder="Enter your full name">
</div>
</div>
<!-- more form elements -->
<button type="button" class="btn btn-success" id="submit">Submit</button>
</form>
</div>
<!-- Booking Summary -->
<!-- Modal content -->
</div>
</section>
</div>
</body>
</html>