#16
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¼ÁÍÂÒ¡àËç¹ ÇÔ¸Õ·Ó¢éÍ 1) ÁÒ¡æàŤÃѺ
·èҹ㴷Óä´é ªèÇÂáÊ´§à»ç¹ÇÔ·ÂÒ·Ò¹ á¡è·Ø¡æ·èÒ¹´éǤÃѺ
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#17
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#15
Áѹ¨ÐÁÕËÅÒªش¨ÃÔ§æËÃͤÃѺ #16 ¹Ö¡ÇèÒ ¨¢¡·. ·Óä´éáÅéÇ«ÐÍÕ¡ ÁÒáͺ´Ù¤ÓµÍº¡Ñ¹¡è͹ àËç¹áÅéÇá·ºÃéͧäËé L I N K ÍéÒ§ÍÔ§:
ãËé $a=\sqrt[3]{\cos\dfrac{2\pi}{9}},b=\sqrt[3]{\cos\dfrac{4\pi}{9}},c=\sqrt[3]{\cos\dfrac{8\pi}{9}}$ ¨Ðä´éÇèÒ $a^3+b^3+c^3=0$ $\dfrac{1}{a^3}+\dfrac{1}{b^3}+\dfrac{1}{c^3}=6$ $abc=-\dfrac{1}{2}$ ãËé $x=a+b+c$ áÅÐ $y=\dfrac{1}{a}+\dfrac{1}{b}+\dfrac{1}{c}$ ¨Ðä´éÇèÒ $x^3=-\dfrac{3}{2}xy+\dfrac{3}{2}$ áÅÐ $y^3=-6xy+12$ á¡éÊÁ¡ÒÃä´é $x=\sqrt[3]{\dfrac{3}{2}\sqrt[3]{9}-3}$ |
#18
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#17 ¤Ø³ Amankris àÃÔèÁ¨Ò¡ $9\theta=2n\pi $ ËÃ×Íà»ÅèÒ¤ÃѺ
¶éÒàÃÔèÁ¨Ò¡µÃ§Í×è¹â»Ã´ªÕéá¹Ð´éǤÃѺ
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#19
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#18
àÃÔèÁẺ¹Ñ鹡çä´é¤ÃѺ ËÃ×ͨÐãªéàÍ¡ÅѡɳìµÃÕ⡳ÍÂèÒ§à´ÕÂÇ¡ç·Óä´éàªè¹¡Ñ¹ |
#20
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ÍéÒ§ÍÔ§:
$\cos 5\theta =\cos 4\theta ~~~~~~~~~ \theta =\dfrac{2n\pi}{9},n=1,2,...$ $16\cos^5 \theta-8\cos^4 \theta -20\cos^3 \theta + 8\cos^2 \theta +5\cos \theta -1=0$ $\cos \dfrac{2\pi}{9}\cos \dfrac{4\pi}{9}\cos \dfrac{6\pi}{9}\cos \dfrac{8\pi}{9}\cos \dfrac{10\pi}{9}=\dfrac{1}{16}$ µÃ§¹Õé¨Ð·ÓÍÂèÒ§äÃãËéàËÅ×Íá¤è $\cos \dfrac{2\pi}{9}\cos \dfrac{4\pi}{9}\cos \dfrac{8\pi}{9}$ÁѹµÔ´µÃ§ $\cos\dfrac{8\pi}{9}$ ¹ÕèáËÅФÃѺ
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#21
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Åͧ´ÙÊÁ¡ÒùÕéÊÔ¤ÃѺ.
$\cos 3A = -\frac{1}{2} = \cos(2n\pi \pm \frac{2\pi}{3})$ $4\cos^3A - 3\cos A = -\frac{1}{2}$ $8\cos^3A - 6\cos A + 1 = 0$ ´Ñ§¹Ñé¹ $\cos \frac{2\pi}{9}\cos \frac{4\pi}{9}\cos \frac{8\pi}{9} = -\frac{1}{8}$ |
#22
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ÍéÒ§ÍÔ§:
Ẻ¹ÕéÁÕËÅÑ¡¡ÒÃÍÂèÒ§äÃËÃ×ͤÃѺ
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#23
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¶éÒÊѧࡵ¡ç¤×ÍÁØÁ·ÕèµÑÇÊèǹà»ç¹¾Ëؤٳ¢Í§ 3 ¡çàÍÒÁÒàÅè¹ä´éẺ¹ÕéÅèФÃѺ.
¡ÅèÒÇâ´Â·ÑèÇä» ¶éÒ $\alpha$ à»ç¹ÁØÁºÇ¡àÅç¡ÊØ´·Õè·ÓãËé $\cos n\theta = \cos \alpha$ áÅéǨÐä´éÇèÒ $\cos \theta = \cos \frac{\alpha}{n}, \cos \frac{2\pi \pm \alpha}{n}, \cos \frac{4\pi \pm \alpha}{n}, ... , \cos \frac{(n-1)\pi \pm \alpha}{n}$ àÁ×èÍ n à»ç¹¨Ó¹Ç¹¤ÕèºÇ¡ 㹡óվÔàÈÉ àÁ×èÍ $n = 3$ ¨Ò¡àÍ¡Åѡɳì $\cos 3\theta = 4\cos^3 \theta - 3cos \theta = \cos \alpha$ ´Ñ§¹Ñé¹ $4\cos^3 \theta - 3cos \theta - \cos \alpha = 0$ ¡ç¨Ðä´éÊٵ÷ÑèÇä»ÇèÒ ÍéÒ§ÍÔ§:
¨´à¡çºäÇéãªé§Ò¹ä´éàÅÂ. ã¹·Õè¹Õé¡çàÅ×Í¡ $\alpha = 2\pi/3$ Å§ä» ¡ç¨Ðä´é¡Ã³Õ੾ÒÐ µÒÁ·Õèµéͧ¡ÒäÃѺ.
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The Lost Emic <<-- ˹ѧÊ×Íà©Å¢éÍÊͺÃдѺ»ÃжÁ¹Ò¹ÒªÒµÔ EMIC ¤ÃÑ駷Õè 1 - ¤ÃÑ駷Õè 8 ªØ´ÊØ´·éÒ ËŧÁÒ 10 ¡Ã¡®Ò¤Á 2011 16:41 : ¢éͤÇÒÁ¹Õé¶Ù¡á¡éä¢áÅéÇ 1 ¤ÃÑé§, ¤ÃÑé§ÅèÒÊØ´â´Â¤Ø³ gon |
#24
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#20
·Õè仵èÍäÁèä´éà¾ÃÒÐÊÃØ»¼Ô´¹Ð¤ÃѺ ´ÙÃÒ¡·Ñé§ËéÒµÑÇ´Õæ¹Ð |
#25
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#24
¼Ô´¨ÃÔ§æ ´éǤÃѺ¢Íº¤Ø³¤ÃѺ ¤ÇÃàÃÔèÁ·Õè 0 ÊԹФÃѺ
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#26
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¢éÍ $2$ µéͧ¢ÍÍÀÑ·ء·èÒ¹¨ÃÔ§æ¤ÃѺ ¼Á¤§¤Ô´ÅÖ¡à¡Ô¹ä»
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site:mathcenter.net ¤Ó¤é¹ |
#27
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ÍéÒ§ÍÔ§:
ËÃ×Íà»ÅèÒ¤ÃѺ |
#28
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#27
äÁèÃÙéÇèÒËÒÁÒÂѧ䧹РáµèäÁèãªèá¹è¹Í¹ |
#29
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¢Í§¤Ø³ Black dragon $x=0$ ¡ç¢Ñ´áÂé§áÅéǤÃѺ
¾Õè nooonuii äÁè¨Óà»ç¹µéͧ¢Íâ·ÉËÃÍ¡¤ÃѺ ¼Ô´¡ç¤×ͼԴ ¶Ù¡¡ç¤×Ͷ١¤ÃѺ (´éÇÂà˵عÕé¼Á¶Ö§ä´é¹Ñº¶×;Õè nooonuii äÇéà˹×ÍËÑÇàÊÁÍ ) $(a_0,a_1,a_2,a_3,a_4,a_5)=(\sin 5x,0,0,0,0,0) , (0,0,0,0,0,1) , (0,\frac{\sin 5x}{\sin x},0,0,0,0) , (0,0,\frac{\sin 5x}{\sin 2x},0,0,0)$ áÅÐÂѧÁÕÍÕ¡ÁÒ¡ÁÒ ¶éÒÍÂÒ¡ãËéÁդӵͺà´ÕÂÇ¡çµéͧ¡ÓªÑºâ¨·Âì¤ÃѺ¼Á
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"ªÑèÇâÁ§Ë¹éÒµéͧ´Õ¡ÇèÒà´ÔÁ!" |
#30
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¢éÍ 2 ⨷Âìà»ç¹áºº¹ÕéËÃ×Íà»ÅèÒ¤ÃѺ
$sin5x=a_0+a_1sinx+a_2sin^2x+a_3sin^3x+a_4sin^4x+a_5sin^5x$ |
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