Re: [積分] 瑕積分一題
※ 引述《xuitechad (fuckyou)》之銘言:
: 1 ____________
: ∫√(1+x)/(1-x) dx =?
: 0
: Ans: π/2+1
令 x = sinθ , 則 dx = cosθ dθ
x = 0 θ = 0
=>
x = 1 θ = π/2
1
∫ √((1+x)/(1-x)) dx
0
π/2
= ∫ (√((1 + sinθ)/(1 - sinθ)))(cosθ) dθ
0
π/2
= ∫ (√(((1 + sinθ)^2)/(1 - (sinθ)^2)))(cosθ) dθ
0
π/2
= ∫ (√(((1 + sinθ)^2)/((cosθ)^2)))(cosθ) dθ
0
π/2 | 1 + sinθ |
= ∫ (|-----------|)(cosθ) dθ
0 | cosθ |
π/2 1 + sinθ
= ∫ (----------)(cosθ) dθ
0 cosθ
(0 ≦ θ ≦ π/2 , sinθ ≧ 0 , cosθ ≧ 0)
π/2
= ∫ 1 + sinθ dθ
0
|π/2
= θ - cosθ |
|0
π π
= (--- - 0) - (0 - 1) = --- + 1
2 2
--
※ 發信站: 批踢踢實業坊(ptt.cc)
◆ From: 140.119.66.27
推
10/12 14:23, , 1F
10/12 14:23, 1F
推
10/12 23:07, , 2F
10/12 23:07, 2F
→
10/12 23:09, , 3F
10/12 23:09, 3F
討論串 (同標題文章)