To permanently delete an obsolete requirement:
 (Delete) in the toolbar or right-click the requirement and click 
                     			 Delete. 
                     		   
                  		   A dialog box appears.
 (Delete) in the toolbar or right-click the requirement and click 
                     			 Delete. 
                     		   
                  		   A dialog box appears. 
                  		   
                  		
               To hide the obsolete requirements again, right-click any requirement in the Requirements tree and click Hide Obsolete Requirements.