<button class="btn btn-primary" type="button" ng-hide="slide === 1" ng-click="back()">{{button1}}</button>
<button class="btn btn-warning" type="button" ng-hide="slide === 4" ng-disabled="myForm.$invalid" ng-click="ok()">{{button2}}</button>
<button class="btn btn-primary" type="button" ng-click="cancel()">{{button3}}</button>
<button class="btn btn-primary" type="button" ng-click="ac.theForm()" ng-disabled="myForm.$invalid">SUBMIT</button>