1
$\begingroup$

This question already has an answer here:

I've found this wonderful identity here.

On the first spot it seems for me true, but I don't have any idea, how could it be proven. In simpler form: "how the hell...?" :-)

$\endgroup$

marked as duplicate by Norbert, Jack D'Aurizio, beep-boop, PhoemueX, Daniel Fischer real-analysis Sep 27 '14 at 16:15

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

Browse other questions tagged or ask your own question.