(3)y=cosx=sin(x+ 元 2 =sinx= sin(x++)=sin(x+2. 22 2 7=-cosx=sin(r+3.n y4)=sinx=sin(x+4. ●●● (sin x)=sin(x +n 同理(cosx))=c0s(x+nz)(3) y=cosx y= −sinx y= −cosx y (4)=sinx ... ) 2 sin(  = x + ) 2 2 sin(   = x + + ) 2 sin( 2  = x +  ) 2 sin( 3  = x +  ) 2 sin( 4  = x +  ) 2 (sin ) sin( ( )  x = x + n n ) 2 (cos ) cos( ( )  x = x + n 同理 n