pure maths

2009-06-08 4:19 am
y=∫[(1-x)/(1+x)]^(1/2) dx
full steps plx

回答 (2)

2009-06-08 5:21 am
✔ 最佳答案
As follows:

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2009-06-08 12:44:01 補充:
你可唔可以再詳細寫下書的方法??
2009-06-09 9:00 am
應是用了 by part;

y=∫[(1-x)/(1+x)]^(1/2) dx
=2∫(1-x)^(1/2) d ((1+x)^(1/2))
=2[(1-x)(1+x)]^(1/2) - 2∫(1+x)^(1/2) d[(1 - x)^(1/2)]
=2[(1-x)(1+x)]^(1/2) - ∫[(1+x)(1-x)]^(1/2) dx

將第一及第四行合併;
積分放在左邊
將左邊積分通分母, 變成 ∫2/ (1- x^2)^(1/2) dx
但始終要 let x = siny etc...

之前的 t formula 方法比較直截.

2009-06-09 01:04:49 補充:
但我個人贊成用有理化.

2009-06-09 01:14:04 補充:
last row should be
2[(1-x)(1+x)]^(1/2) + ∫[(1+x)(1-x)]^(1/2) dx

then
將左邊積分通分母, 變成 ∫-2x/ (1- x^2)^(1/2) dx


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