y=(根号2)*sin[x+(π/4)]
当[x+(π/4)]=(π/2)+2kπ,
解得x=(π/4)+2kπ.k=0,1,……时,y达到最大(根号2)
当[x+(π/4)]=-(π/2)+2kπ,
解得x=-(3π/4)+2kπk=0,1,……时,y达到最小(负根号2)
哈哈