易知,1-cos2x=2sin²x≥0.故y=4cosx+(3√2)|sinx|.由柯西不等式可知,18≥16+2sin²x=(4cosx)²+[(3√2)|sinx|]²≥[4cosx+(3√2)|sinx|]²=y².===>|y|≤√18.===>-3√2≤y≤3√2.等号仅当|...