用换元法求定积分∫1/1+√x dx上限是1下限是0

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用换元法求定积分∫1/1+√x dx上限是1下限是0

用换元法求定积分∫1/1+√x dx上限是1下限是0
用换元法求定积分∫1/1+√x dx上限是1下限是0

用换元法求定积分∫1/1+√x dx上限是1下限是0
见图

令根号x=t,∫1/1+t dt^2=2-ln2

∫(0->1)1/(1+√x) dx
let
√x = (tana)^2
[1/(2√x)]dx = 2tana(seca)^2 da
dx = 4(tana)^3(seca)^2da
x=0, a=0
x=1, a=π/4
∫(0->1)1/(1+√x) dx
=∫(0->π/4)[1/(seca)^2]4(tana)^3(seca...

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∫(0->1)1/(1+√x) dx
let
√x = (tana)^2
[1/(2√x)]dx = 2tana(seca)^2 da
dx = 4(tana)^3(seca)^2da
x=0, a=0
x=1, a=π/4
∫(0->1)1/(1+√x) dx
=∫(0->π/4)[1/(seca)^2]4(tana)^3(seca)^2da
=∫(0->π/4) 4(tana)^3 da
=-∫(0->π/4) [4(1-(cosa)^2)/(cosa)^3 ] dcosa
=4[ 1/[2(cosa)^2] + ln|cosa| ](0->π/4)
=4( 1-(1/2)ln2-1/2 )
=2(1-ln2)

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