lim (cosx-sinx)/cos2x x→π/4

问题描述:

lim (cosx-sinx)/cos2x x→π/4

(cosx-sinx)/cos2x=(cosx-sinx)/(cos^2x-sin^2x)=1/(sinx+cosx)
lim (cosx-sinx)/cos2x x→π/4=√2/2