Tabs at the top AND at the bottom of a page?

In case of several very long pages organized by tabs, is it better to repeat tabs at the bottom or to have a "Go to top" button?

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Answer

Rather than have really long pages inside the tabs, fix the height of the tabs so that they occupy the full height of the screen and use a scroll viewer inside the tabs to display the content:

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This way the tabs are always visible at the top of the screen where the user expects them to be. If there's enough height the scroll bar should be hidden.