y=sin(x/2)+cos(x/2)=(√2)sin[(x/2)+(π/4)].由-2π＜x＜2π,====>-3π/4＜(x/2)+(π/4)＜5π/4.可设t=(x/2)+(π/4).===>y=(√2)sint,(-3π/4＜t＜5π/4).易知,在(-3π/4,5π/4)上,函数y=(√2)sint的递增区间为[-π...