Try this:
<!DOCTYPE html>
<html>
<head>
<script src= "http://ajax.googleapis.com/ajax/libs/angularjs/1.3.14/angular.min.js"></script>
</head>
<body>
<div ng-app="">
<form>
<input id="first" type="radio" name="content" ng-model="content" value="first">First
<br />
<input id="other" type="radio" name="content" ng-model="content" value="fifth">Fifth
</form>
<input type="text" ng-show="content != 'fifth'">
</body>
</html>
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