數學高微的題目

2010-06-15 7:52 am
已知:F(x) = ∫[0~∞] e^[-t^2] cos xt dt for x 屬於R,其中F’(x) = -1/2x*F(x) 且 F(x) = {[√(pi)] * e^[-(x^2)/4]} /2。
請利用上述條件,證明:
Let G(x) = ∫[0~∞] e^[-t^2] sin xt dt for x 屬於R,show that G(x) = e^[-(x^2)/4]∫[0~x] e^[t^2/4] dt 。
更新1:

想請教G(x)的答案差0.5倍的過程,謝謝這位大師

更新2:

只要有相似的證明過程,都可以回答,感謝各位

回答 (2)

2010-06-16 8:14 pm
✔ 最佳答案
真是意想不到我寫的http://tw.knowledge.yahoo.com/question/article?qid=1710011701526和http://tw.group.knowledge.yahoo.com/ignored-knowledgeunion/article/view?aid=6終於可以大派用場,我還以為課程會因為答案的形式而不敢出。

2010-06-15 06:18:04 補充:
又不能怪它的,因為這題的答案與imaginary error function(http://mathworld.wolfram.com/Erfi.html)有密切關係,若一不小心把題目出成「化簡∫[0~∞] e^[-t^2] sin xt dt。」,那注定會被人投訴。

2010-06-15 06:28:12 補充:
事實上,G(x)不是用F(x)的結果去求而是用求F(x)的方法去求,所以題目是用「條件」一詞而不是用「結果」一詞,而且題目故意要寫F(x)的描述是要提醒我們本題要用「砌de法」去解決。

2010-06-16 12:14:18 補充:

圖片參考:http://i212.photobucket.com/albums/cc82/doraemonpaul/yahoo_knowledge/improperintegral/goodimproperintegral0.jpg


圖片參考:http://i212.photobucket.com/albums/cc82/doraemonpaul/yahoo_knowledge/improperintegral/goodimproperintegral1.jpg


圖片參考:http://i212.photobucket.com/albums/cc82/doraemonpaul/yahoo_knowledge/improperintegral/goodimproperintegral2.jpg


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圖片參考:http://i212.photobucket.com/albums/cc82/doraemonpaul/yahoo_knowledge/improperintegral/goodimproperintegral4.jpg


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圖片參考:http://i212.photobucket.com/albums/cc82/doraemonpaul/yahoo_knowledge/improperintegral/goodimproperintegral6.jpg


圖片參考:http://i212.photobucket.com/albums/cc82/doraemonpaul/yahoo_knowledge/improperintegral/goodimproperintegral7.jpg


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圖片參考:http://i212.photobucket.com/albums/cc82/doraemonpaul/yahoo_knowledge/improperintegral/goodimproperintegral9.jpg

參考資料:
method same as http://tw.knowledge.yahoo.com/question/article?qid=1710011701526 and http://tw.group.knowledge.yahoo.com/ignored-knowledgeunion/article/view?aid=6 + my wisdom of maths
2010-06-15 8:51 am
G(x)的答案差0.5倍!

2010-06-15 00:52:09 補充:
G(x)不用F(x)的結果即可得!


收錄日期: 2021-04-30 14:56:27
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20100614000010KK09489

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