例4设y=sinx,求y!m), 解y’=c0sx=si(r×个 2 y"=cos(x+o=sin(x+4+1=sin(x+2 T 22 y=c0s(x+2.2 2 )=sin(x+34 (n) y=sIn(xt n 2 同理可得(cosx))=cos(x+n 2 上页例4 sin , . (n) 设 y = x 求y 解 y = cos x ) 2 sin(  = x + ) 2 cos(  y = x + ) 2 2 sin(  +  = x + ) 2 sin( 2  = x +  ) 2 cos( 2  y = x +  ) 2 sin( 3  = x +   ) 2 sin( ( )  y = x + n n ) 2 (cos ) cos( ( )  x = x + n n 同理可得