CRM 2011 JS: Hide and Show tab

This is how to hide and show tab

Hiding tab
Xrm.Page.ui.tabs.get(tabindex).setVisible(false);
or
Xrm.Page.ui.tabs.get("tabname").setVisible(false);

Showing tab
Xrm.Page.ui.tabs.get(tabindex).setVisible(true);
or
Xrm.Page.ui.tabs.get("tabname").setVisible(true);