It did say find the derivative for part (a) ig - but I do not know where to go one from there....
This is how I thought abt the question;
The derivative is 0, this should imply that the function is constant for certain values. Clearly x =/ 0 as from tan^-1(x) so the domain would be split into x > 0 and x < 0.
What I'd do now is I would test for the domain x < 0 and x > 0 so I would test for x = 1 and x = -1. When you test x =1, you get pi/2 and x = -1 you get - pi/2. Since the derivative is 0, for x > 0, the function outputs pi/2 and likewise for x < 0, the function outputs - pi/2 and there is a discontinuity at x = 0.
So you would get two lines, y = pi/2 for x > 0 and y = -pi/2 for x < 0 with open circles for both pi/2, - pi/2 at x = 0.