Draw a blank graph (x-y axis), then start plotting points until you find the straight-line (e.g. plot at least 2 points, then get a straight-edge and connect the dots):
(x,y)
(0,0)
(1,-2)
(2,-4)
(-1,2)
(-2,4)
-2
12
-2
8
8
That line is [ y = 2 cos(2x) ].
3
This site is not suitable for graphs.
No.
10
The domain of y = 2x is [0, +infinity].
Yes, that is a shifted tanX graph, just as you would shift any graft.