求函数的微分dy 1)y=e^(-2x)*cos3x ;2)y=(x^2+1)/x+1
问题描述：
求函数的微分dy 1)y=e^(-2x)*cos3x ;2)y=(x^2+1)/x+1
答
1) dy = d(e^(-2x)*cos3x) = [-3sin3xe^(-2x) - 2cos3xe^(-2x)]dx 2) dy = d((x^2+1)/(x+1)) = [2x(x+1) - (x^2+1)]/(x+1)^2 = (x^2+2x-1)/(x+1)^2 = 1 - [2/(x+1)^2]