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Math trig problem

  1. Oct 5, 2005 #1
    i have to show that
    [tex] \sin \left( 1/9\,\pi \right) \sin \left( 2/9\,\pi \right) \sin \left(

    1/3\,\pi \right) \sin \left( 4/9\,\pi \right) = 3/16 [/tex]

    i ve tried so many things, and i couldnt get to 3/16 :confused: , does anyone have any hints that are gonna help me solve problems in that kind!? thanks!
  2. jcsd
  3. Oct 5, 2005 #2


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    It works for me. What have you done?
  4. Oct 5, 2005 #3
    Well, i have remplaced sin(2pi/9) by sin(3pi/9 - pi/9) and sin(3pi/9) by sin(4pi/9 - pi/9) and so on, and used the relation sin(a+b)=sina cosb + sinb cos a. so everything will have sin(pi/9) in it, so i can factor with that to get something helpful. but i guess i just messed everything up, and i dont know what relation i can use to get closer the 3/16 or what method i should use
  5. Oct 6, 2005 #4
    never mind, i got it :smile:
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