Sometimes when you login to Central Administration in SharePoint you cannot create, extend, or delete web application because the buttons in ribbon are disabled or grayed out. The same applies to the Authentication Providers button and if you hover mouse over this button this is what you see: This looks weird because you may be the farm administrator but still these buttons are grayed out. This can be solved by running Internet Explorer with elevated privileges (Right Click - Run as Administrator) or by accessing Central Administration website from Start Menu. Here is how you can do it from Windows Server 2012:
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