Solved: tan⁡9° - tan⁡27° - tan⁡63° + tan⁡81°

Here one of math trigonometri's question solved : tan⁡9° - tan⁡27° - tan⁡63° + tan⁡81°  ..

 

Here the support link to explain where the sin 54 and sin 18 value came from...Pentagon

Credit to : http://in.answers.yahoo.com/question/index?qid=20091002055257AAZDdPV

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I don't have any intention of plagiarism... I just try to make the more access, more source... because I, myself also encounter of hard to find source (some question I cannot found in Internet).

Updated!!!!: here another way to prove!!

Note : sin 72 = sin 108 also sin 144 = sin 36 because sin (180-72) = sin 72 also sin (180-36) = sin 36!

Credit to : Yudi Rizky as contributor for better idea.!!!

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