例2.2.5证明(tanx)}'=sec2x, 证:(a知xy- 乙O3=(sin x)cosx二sin (cosx' cos2 x cos2 x +sinx =sec2 x cos-x 类似可证: (cotx)'=-csc2x,(secx)'=secxtanx. (cscx)'=-cscxcotx. BEIJING UNIVERSITY OF POSTS AND TELECOMMUNICATIONS PRESS 目录上 下负返回 结束目录 上页 下页 返回 结束 例2.2.5 证明 (tan ) sec , 2 x x 证: (csc x) csc x cot x . x x x cos sin (tan ) x 2 cos (sin x)cos x sin x (cos x) x 2 cos x 2 cos x 2 sin x 2 sec 类似可证: (cot ) csc , 2 x x (sec x) sec x tan x