#1
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͹ءÃÁ ¤ÃÒººº
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$1 - \frac{1}{2} + \frac{1}{3} - \frac{1}{4} + \frac{1}{5} - \frac{1}{6} + ... $ àËç¹à¤éÒÇèҵͺ ln 2 (⨷Âìá¢è§¢Ñ¹ ãËéàÇÅÒ¤Ô´á¤è 20 ÇÔ¹Ò·Õ !) ¤Ô´ÇèÒ¤§ÁÕ·ÃÔ¤ÍÐäëѡÍÂèÒ§ ¤Ô´äÁèÍÍ¡¤ÃѺ ã¤ÃÃÙéªèǺ͡´éǤÃѺ
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#2
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¶éÒà»ç¹â¨·ÂìÃдѺÁ.»ÅÒ¨ÃÔ§æ ¼ÁÇèÒ¢é͹Õé¤ÇèѴÍÂÙèã¹ËÁÇ´¤ÇÒÁÃÙéÃͺµÑǤÃѺ
à¾ÃÒÐà·¤¹Ô¤·Õèãªé㹡ÒÃËҤӵͺ͹ءÃÁ¹Õéà»ç¹ÃдѺÁËÒÇÔ·ÂÒÅÑ ¶éÒäÁèÃÙé¨Ñ¡ÁÒ¡è͹¤Ô´ÀÒÂã¹ 20 ÇÔ¹Ò·ÕäÁèä´éËÃÍ¡¤ÃѺ
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#3
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ÃÙéÊÖ¡µéͧãªé Ẻ¹ÕéÍèÐ
$$\int_{1}^{\infty}(\frac{1}{x}-\frac{1}{x+1})\,dx$$ ÃÖ»ÅèÒÇËÇèÒ
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#4
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àÍÍ áÅéÇ·Óä§ËÃÍ ¤ÃѺ áÊ´§ãËé´Ù·Õä´éÁÑé¤ÃѺ
ÂѧäÁèà¤ÂÍÔ¹·Ôà¡Ãµ¶Ö§Í¹Ñ¹µ×ÁÒ¡è͹àÅÂ
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#5
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ãªé¡ÒáÃШÒÂ͹ءÃÁà·àÅÍÃì¤ÃѺ
$\ln{(1+x)}=x-\dfrac{x^2}{2}+\dfrac{x^3}{3}-\dfrac{x^4}{4}+\cdots$
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site:mathcenter.net ¤Ó¤é¹ |
#6
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ÍéÒ§ÍÔ§:
= =a ÊèǹÇÔ¸ÕÍÔ¹·Ôà¡Ãµ¹Ñé¹ ãËéÅͧ෤ ÅÔÁÔµ à¢éÒÊÙè ÍÔ¹¿Ô¹ÔµÕé ´Ù¤ÃѺ
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#7
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àÍÍ ¢Íâ·É¨ÃÔ§æ¤ÃѺ
äÁèà¢éÒã¨ÍèФÃѺ ªèÇÂáÊ´§ÇÔ¸Õ·ÓãËé´Ù˹èÍÂä´éÁÑé¤ÃѺ
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#8
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ÍéÒ§ÍÔ§:
$$= \lim_{a \to \infty} \int_{1}^{a}(\frac{1}{x}-\frac{1}{x+1})\,dx $$ $$= \lim_{a \to \infty} [\ln x - \ln (x+1)]_{1}^{a} $$ $$= \lim_{a \to \infty} ((\ln a - \ln (a+1))- (\ln1 - \ln2)) $$ $$= \lim_{a \to \infty} (\ln\frac{a}{a+1}+\ln2) $$ $$= \ln2$$
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àÁ×èÍäÃàÃÒ¨Ðà¡è§àÅ¢¹éÒÒÒÒÒÒ ~~~~ T T äÁèà¡è§«Ñ¡·Õ ·Óä§´Õ 19 ¡Ñ¹ÂÒ¹ 2009 23:17 : ¢éͤÇÒÁ¹Õé¶Ù¡á¡éä¢áÅéÇ 1 ¤ÃÑé§, ¤ÃÑé§ÅèÒÊØ´â´Â¤Ø³ -InnoXenT- |
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