Also i don't get what does 1-1 mean ?
t(x) = arctan (2x)
I'm not sure if this is right. But i got domain= all real x, where x doesn't = 0. I have no idea about the range.
x = 0 is OK for the domain! arctan(0) = 0 and all is well. The domain is all real x.
The range is (-pi/2, pi/2). That's easy to see if you consider the domain of the inverse of t(x), that is, (1/2) tan (x) ....