∫x/√(4-x^2)dx
=-(1/2)∫d(4-x^2)/√(4-x^2)
=-(1/4)√(4-x^2)+C=-(1/2)∫d(4-x^2)/√(4-x^2)这一步怎么求的呢，求解，谢谢xdx=d(x^2)=-(1/2)d(-x^2)=-(1/2)d(4-x^2)你得从求导数来看：[-(1/2)(4-x^2)]'=x，所以d[-(1/2)(4-x^2)]'=dx