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tanjung

  • 2 years ago

Help... Prove that sin36 degrees = sqrt[10 - 2*sqrt(5)]/4

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  1. micahwood50
    • 2 years ago
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    HINT: 180º/5 = 36º

  2. tanjung
    • 2 years ago
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    next, what's formula using i do

  3. micahwood50
    • 2 years ago
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    Seems like it won't help. Try this, using the formula sin (a + b) = cosa sinb + cosb sin a sin36º = 2 sin18º cos18º = 2 cos72º sin72º

  4. tanjung
    • 2 years ago
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    ok, i know that formula.. but i think we get the new problem... because sin/cos 18 or sin/cos 72 not eassy to get.. it's very difficul, right ?

  5. micahwood50
    • 2 years ago
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    It seems so. Bump your question to get more helps. Maybe someone can help you with this.

  6. tanjung
    • 2 years ago
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    ok, thanks...

  7. tanjung
    • 2 years ago
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    @cwrw238 , @experimentX , @estudier , @Hero , @Zarkon , @sauravshakya , @all... help me please, how to get it

  8. tanjung
    • 2 years ago
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    any idea guys ?

  9. ajprincess
    • 2 years ago
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    |dw:1350231015827:dw||dw:1350231152168:dw| Use quadratic formula |dw:1350231253477:dw| |dw:1350231349862:dw|

  10. experimentX
    • 2 years ago
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    @ajprincess try this|dw:1350231460480:dw|

  11. tanjung
    • 2 years ago
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    ok, i get |dw:1350231717622:dw|

  12. tanjung
    • 2 years ago
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    next ?

  13. tanjung
    • 2 years ago
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    upss. sorry, divided 8

  14. ajprincess
    • 2 years ago
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    |dw:1350231971343:dw||dw:1350232035700:dw|

  15. ajprincess
    • 2 years ago
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    @experimentX I tried bt it is a bit complex. cos sin3x=sin108.

  16. ajprincess
    • 2 years ago
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    Getting it @tanjung?

  17. experimentX
    • 2 years ago
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    this should be simpler ... sin(3x) = sin(2x)

  18. tanjung
    • 2 years ago
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    not yet, what should i do after that

  19. experimentX
    • 2 years ago
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    since this is just double angle and triple angle ... change everything back to sin ... and remove all roots and try to factorize it.

  20. ajprincess
    • 2 years ago
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    |dw:1350232254804:dw|

  21. tanjung
    • 2 years ago
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    so, just take positive sign in sqrt ?

  22. tanjung
    • 2 years ago
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    i know that +- it means there are two number here. what about u for it

  23. mukushla
    • 2 years ago
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    with positive sign u have sin 36>1 thats impossible

  24. ajprincess
    • 2 years ago
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    |dw:1350233305717:dw|

  25. tanjung
    • 2 years ago
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    oh yea, i understand now... thank u very much for ur help , @ajprincess and @mukushla

  26. ajprincess
    • 2 years ago
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    yw:)

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