Question

What are the important points to graph `y=sin x-1`?

Answer 1

A al sine graph `y=AsinBx` has amplitude `A` and period `T=(2pi)/B`.
So in this case `A=1` and `T=2pi`. This means that it takes `2pi` radians to complete 1 full cycle.
However, the graph is now displaced 1 unit down so instead of `[-1,1]`, the new range now becomes `[-2,0]`.
The domain remain `RR`.

Graphically

graph{sinx-1 [-7.02, 7.025, -3.51, 3.51]}