y=（cosx/|cosx|）+（2sinx/|sinx|）当x∈（2kπ,2kπ+π/2）时,（k∈Z）y=3当x∈（2kπ+π/2,2kπ+π）时,y=-1+2=1当x∈（2kπ+π,2kπ+3π/2）时,y=-3当x∈（2kπ+3π/2,2kπ+2π）时,y=-1故y的值域为[-3,-1,1,3]...