大学高等数学 洛必达法则求lim x→ π ln cos(x- π)/(π -x)^2

Question

如题所述

Answer 1

设t=x-π，则lim=lim(cost-1)/t^2=lim-2(sin(t/2)/t)^2=-2(1/2)^2=-1/2
洛必达=lim(-sin(x-π）/cos(x-π）)/2(x-π）=-1/2