angular 1 js, there are no way to remove class : I trying search many to many here but i can not find result for `removeClass` in angular js.

here my example code

    <form name="myform" ng-class="plus">
        //...
	    <button ng-click="save()">click</button>
    </form>

and my angular

    $scope.add_page = function(){
		$scope.myform.removeClass(plus);//what i try but not work
	}

any suggest how to removed class or remove attribute ? 