x+2⼀根号x^2-2x+4求不定积分

2024-11-30 12:30:31
推荐回答(1个)
回答(1):

你的表达可能有点问题,是不是想求 ∫[(x+2)/(x^2-2x+4)]dx ?  
若是这样,则方法如下:
原式=∫{(x-1+3)/√[(x-1)^2+3]}d(x-1)。
令x-1=√3tanθ,则:tanθ=(x-1)/√3,dx=[√3/(cosθ)^2]dθ,
∴容易求出:cosθ=√3/√[3+(x-1)^2)],sinθ=(x-1)/√[3+(x-1)^2)]。
∴原式=∫{(√3tanθ+3)/√[3(tanθ)^2+3]}[√3/(cosθ)^2]dθ
   =∫[(√3tanθ+3)/cosθ]dθ
   =√3∫[sinθ/(cosθ)^2]dθ+3∫[1/cosθ]dθ
   =-√3∫[1/(cosθ)^2]d(cosθ)+3∫[1/(cosθ)^2]d(sinθ)
   =√3/cosθ+(3/2)∫{[(1+sinθ)+(1-sinθ)]/[1-(sinθ)^2]}d(sinθ)
   =√[3+(x-1)^2]+(3/2)∫[1/(1-sinθ)]d(sinθ)
    +(3/2)∫[1/(1+sinθ)]d(sinθ)
   =√(x^2-2x+4)-(3/2)ln(1-sinθ)+(3/2)ln(1+sinθ)+C
   =√(x^2-2x+4)-(3/2)ln|1-(x-1)/√[3+(x-1)^2)]|
    +(3/2)ln|1+(x-1)/√[3+(x-1)^2)]|+C
   =√(x^2-2x+4)+(3/2)ln|√(x^2-2x+4)+x-1|
    -(3/2)ln|√(x^2-2x+4)-x+1|+C

注:若原题不是我所猜测的那样,则请你补充说明。