Let

- Find all points such that ;
- Determine the intervals on which is monotonic by examining the sign of ;
- Determine the intervals on which is monotonic by examining the sign of ;
- Sketch the graph of .

- We take the derivative,
Thus,

- is increasing if and decreasing if .
- Taking the second derivative,
Thus, is increasing for all .

- We sketch the curve,

In c) it should be 1/3 cos2x.