举报
qq专用MJ01
你题目写错了 令y=ln(cosx/cos2x)^(1/x^2)=(1/x^2)ln(cosx/cos2x)=(1/x^2)ln[1+(cosx-cos2x)/cos2x] limy=lim 1/x^2 *(cosx-cos2x)/cos2x =lim1/x^2 *(cosx-cos2x) =lim(cosx-cos2x)/x^2 =lim(sinx-2sin2x)/2x =lim(sinx-4sinxcosx)/2x =limsinx(1-4cosx)/2=-3/2 原极限=e ^(-3/2)