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Find the numerical value of $$\tan(3\pi/11)+4\sin(2\pi/11)$$ without actually calculating the values. How to start? Please help.

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    see here http://mathworld.wolfram.com/TrigonometryAnglesPi11.html – Dr. Sonnhard Graubner May 13 '15 at 17:41
  • Try converting all of the trigonometric functions to functions involving pi/11 using multiple angle formulae – Hiten May 13 '15 at 17:45
  • @Dr.SonnhardGraubner : There's not a word on how to obtain the result of (13) – Alexey Burdin May 13 '15 at 17:45
  • I want to know the method... –  May 13 '15 at 17:57
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    this will be help https://www.ocf.berkeley.edu/~wwu/cgi-bin/yabb/YaBB.cgi?board=riddles_hard;action=display;num=1167686768 – Dr. Sonnhard Graubner May 13 '15 at 17:58
  • I want a simple trigonometry proof... These links don't help –  May 13 '15 at 18:00
  • @You-know-me, Related : http://math.stackexchange.com/questions/11246/how-to-prove-that-tan3-pi-11-4-sin2-pi-11-sqrt11, http://math.stackexchange.com/questions/578286/how-prove-this-tan-frac2-pi134-sin-frac6-pi13-sqrt132-sqrt13 – lab bhattacharjee May 14 '15 at 05:17
  • Yeah, it is related. But I want a simple trigonometry proof. And the one given is totally out of the box. I mean, there has got to be a normal proof starting from my LHS and ending at RHS. –  May 14 '15 at 06:10

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