#1
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µÃÕ⡳¤ÃѺ
$1sin^2 1^{\circ} + 2sin^2 2^{\circ} + 3sin^2 3^{\circ} + 4sin^2 4^{\circ} +...+180sin^2 180^{\circ} $
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#2
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Åͧ¨Ñº¤Ùè´Õæ¤ÃѺ
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#3
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ªèÇÂÍÕ¡¹Ô´¹Ö§
$\sin(\pi-A)=\sin A$ áÅéÇÅͧ¨Ñº¤ÙèÍÂèÒ§·Õè¤Ø³ Amankris ºÍ¡¤ÃѺ
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no pain no gain |
#4
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ÍéÒ§ÍÔ§:
¨Ðä´é sin 1 = sin 179 $ \therefore sin^2 1 + 179sin^2 179 = sin^2 1 + 179 sin^2 1 = 180sin^2 1$ $\therefore $ $1sin^2 1^{\circ} + 2sin^2 2^{\circ} + 3sin^2 3^{\circ} + 4sin^2 4^{\circ} +...+180sin^2 180^{\circ} $ $= (180sin^2 1 + 180sin^2 2 + ... + 180sin^2 89) + 90sin^2 90 + 180sin^2 180$ $= 180(sin^2 1 + sin^2 2 +...+sin^2 89) + 90$ $co-function$ $=180(sin^2 1 + sin^2 2 +...+cos^2 45 + cos^2 44 +...+cos^2 2 +cos^2 1) +90$ $=180(44(1)+0.5)+90$ $=180(44) + 90 +90$ $=8100 $ Å×Áãªé co-function ==" 04 ¡Ã¡®Ò¤Á 2011 21:36 : ¢éͤÇÒÁ¹Õé¶Ù¡á¡éä¢áÅéÇ 6 ¤ÃÑé§, ¤ÃÑé§ÅèÒÊØ´â´Â¤Ø³ CHAOS |
#5
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#4
à¡×ͺ´ÕáÅéǤÃѺ ¾ÅÒ´ÍÐäúҧÍÂèҧ仹Р|
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