Moderator Edit: This question provoked some discussion which, while off-topic, has the potential for interesting debate and further discussion. I have therefore copied the question to the Chat Room (so that the context of the discussion is not lost) and moved the off-topic replies to this thread. Please feel free to continue the off-topic discussion -
in this thread.
If you have something to contribute regarding the solution, don't post it here. Post it at
trigo-sum.
Calculate this sum : 
