例2f(x)=x3+4cox-sin2,求/(x)(2 fW f(x)=(x3)+(4cos x)-(sin ) 3x2-4sin x结束 例 2 2 ( ) 4cos sin 3  f x =x + x−  求 f (x)及 ) 2(  f   4 43 ) 2 ( 2  =  −  f  解 ) 2 ( ) ( ) ( 4cos ) (sin 3  = + −   f x x x = 3 x 2 −4sin x  解