Graph y0 = cos(x)
Graph y1 = 3cos(x) -- Just change the vertical limits from [-1,1] to [-3,3]. Done
Graph y2 = 3cos(x) - 2 -- Just change the vertical limits from [-3,3] to [-5,1]. Done
Graph y3 -- Oh, you're not going to make me do ALL the work, are you? You do this one.
Of course, when you are done, you may wish to find the x- and y- coordinate axes. They did wander around a bit.