JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://code.angularjs.org/1.2.26/angular.js"></script>
<div ng-controller="MyCtrl">

<form name="personForm" ng-submit="submit(personForm)">
    
    Gender: 
    <label>
        <input type="radio" ng-model="male" ng-value="true" ng-required="male!==false && male!==true"/>
        Male
    </label>
    <label>
        <input type="radio" ng-model="male" ng-value="false"/>
        Female
    </label>
    
    <br/>
    <br/>
    
    <button type="submit" ng-disabled="personForm.$invalid">Submit</button>
    
</form>
    
</div>

JavaScript

var myApp = angular.module('myApp',[]);

function MyCtrl($scope) {
    $scope.male = undefined; // intentionally not set

    $scope.submit = function(form) {
        if (form.$valid)
            window.alert("The form is valid!");
    };
}