The function is .

Compare the given function with  y = a cos (bx - c) + d.

Here, , so the shift is 3 units downward.

Amplitude is  .

And period  .

The interval corresponds to one cycle of the graph.

Divide this interval into four equal parts to produce the key points. 

\ x \	\ \	\ (x, y) \
\ \	\ \
\ \	\ \	\ \
\ \	\ \	\ \
\ \	\ \	\ \
\ \	\ \	\ \

1). Draw the co-ordinate plane.

2). Plot the key points.

3). Sketch the graph, connected through those key points with a smooth curve.

Graph :

The graph of is :