lim(x→0) (cos2x)^(1/x^2)先换成e指数的形式=lim e^[(1/x^2)lncos2x]=e^[lim (1/x^2)ln(1+cos2x-1)]ln(1+x)~x等价无穷小替换=e^[lim (1/x^2)(cos2x - 1)]{cos2x-1 -(2x)^2=-4x^2}=e^[(1/x^2)(-4x^2)]=e^(-4)...
