I am new in angularJs .

This is my bit level view

<input type=text ng-model=todoName size=30

            placeholder=Add Your Name>

        <input type=text ng-model=todoAge size=30

            placeholder=Add Your Age>

        <input type=hidden ng-model=todoId />

        <form style=display:'?????????' ng-submit=addTodo()>

            <input class=btn-primary type=submit value=add>

        </form>

         <form style=display:'?????????' ng-submit=addTodo()>

            <input class=btn-primary type=submit value=update>

        </form>

and this is my angularjs bit level coding

$scope.DisplayUpdate = none;

I have one screan for manage student details, i want to show add button when first time at this time hide update button , and when update time to show update button and at this time add button was need to hide .

see this line for set to hide and show details in script side using angular js : $scope.DisplayUpdate = none;

How to i set this value in my button style ?

 <form style=display:'?????????' ng-submit=addTodo()>

                <input class=btn-primary style=display:'?????????' type=submit value=add>

            </form>