求积分∫(arctan(1/x)/(1+x^2))dx
2个回答

嘿嘿,其实这题很简单.

令y = 1/x、x = 1/y、dx = - 1/y² dy

∫ [arctan(1/x)]/(1 + x²) dx

= ∫ arctany/(1 + 1/y²) * (- 1/y² dy)

= ∫ arctany * y²/(1 + y²) * (- 1/y²) dy

= - ∫ arctany/(1 + y²) dy

= - ∫ arctany d(arctany)

= (- 1/2)(arctany)² + C

= (- 1/2)[arctan(1/x)]² + C