例2.求证(tanx)=sec2x,(cscx)/=-cscxcotx. 证：((tanx)'= Sinx = (sinx)'cosx-sinx(cosx) cosx cos2 x cos2x+sinx=sec2x COsx n) sin2x sin2x =-cscxcotx 类似可证：(cotx)'=-csc2x,(secx)}=secxtanx.(csc x) =        sin x 1 x 2 sin = − (sin x) x 2 sin = 例2. 求证 证:         = x x x cos sin (tan ) = x 2 cos (sin x)cos x − sin x (cos x) = x 2 cosx 2 cos x 2 + sin x 2 = sec − cos x = −csc xcot x 类似可证: (cot ) csc , 2 x  = − x (sec x) = sec x tan x . 机动 目录 上页 下页 返回 结束