Y = the range of | SiNx | - 2sinx? When SiNx > = 0, y = | SiNx | - 2sinx = - SiNx, the range is [- 1,1] When SiNx < 0, y = - SiNx - 2sinx = - 3sinx Why is the value range of the final answer: [- 1,3]?

Y = the range of | SiNx | - 2sinx? When SiNx > = 0, y = | SiNx | - 2sinx = - SiNx, the range is [- 1,1] When SiNx < 0, y = - SiNx - 2sinx = - 3sinx Why is the value range of the final answer: [- 1,3]?

It is true that y = - SiNx can be obtained from SiNx > = 0, but since it is under the condition of SiNx > = 0, - SiNx should belong to [- 1,0]
Similarly, when SiNx < 0, y = - 3sinx, - 3sinx belongs to (0,3]
The value range of the two is: [- 1,3]. That's right~