1、sinx≥0
y=-sinx
∴y∈[-1,0]
sinx<0
y=-3sinx
∴y∈(0,3]
2、x≥0①x∈[2kπ,2kπ+π] k=0,1,2. y=2sinx ∴y∈[0,2]
②x∈[2kπ+π,2kπ+2π] k=0,1,2. y=0
x<0 ①x∈[2kπ,2kπ+π] k=0,-1,-2.y=0
②x∈[2kπ+π,2kπ+2π] k=0,-1,-2. y=-2sinxy∈[-2,0]
∴y∈[-2,2]