Re: [積分] 極限
原文恕刪
x 2
let f(x)=∫ cos t dt and g(x)=x
0
then f(x)→0 and g(x)→0 as x→0
f'(x)
since lim ------
x→0 g'(x)
d x 2
--- ∫ cos t dt
dx 0
=lim ----------------------
x→0 d
--- x
dx
2
= lim ( cos x )
x→0
=1 (exist!!)
and g'(x)=1≠0 on an open interval containing 0
By L'Hospital Rule
f(x) f'(x)
so lim ---- = lim ------ = 1
x→0 g(x) x→0 g'(x)
那請問這樣寫是正確的嗎?
最後附上L'Hospital Rule wiki
http://en.wikipedia.org/wiki/L'H%C3%B4pital's_rule
--
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◆ From: 140.113.62.161
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感謝a大的補充!!
回應y大的問題:
也不是說一定要用,只是我認為能從各個角度來解決問題是很棒的一件事,定義的方法我
知道是正確的,但並不是所有修微積分的學生都能想到,我想大多數的人看到0/0也會
想到羅必達。或許就講講最簡單的例子就好(畢氏定理或稱商高定理),也是有無數人用
各種方法去解決它,我不認為這些其他的方法是無意義的,相反的,反而能開拓視野,讓
人可以從更多的角度來了解它、欣賞它。
※ 編輯: sm008150204 來自: 140.113.62.161 (12/20 11:15)
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我知道定義是對的,不過我現在想了解的只是
「是否能用羅必達做這個問題?」
※ 編輯: sm008150204 來自: 140.113.62.161 (12/21 01:34)
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感謝大家的回覆!!
※ 編輯: sm008150204 來自: 140.113.62.161 (12/21 23:13)
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