@Kitonum 
restart: with(plots):
inequal({y < 2, y >= x^2+1, (x-1)^2+(y-1)^2 <= 16}, x = -5 .. 8, y = -6 .. 6, optionsfeasible = (color = grey));
about syntax will cause part of circles missing. what should I do so that able to plot complete circle?

@Carl Love Thanks Carl. I finally get it

@Carl Love by applying the command above, I still cannot see the value of y = 4 when x = 1 in graph generated by using plot command. what others parameter that needed to add into plot command.

@Carl Love 

Thanks, However, as I understand above command is for Maple 2015. How about the command for Maple 18?

Thanks  a lot.

As refer to the command on piecewise function

http://www.maplesoft.com/support/help/Maple/view.aspx?path=piecewise

With the piecewise function it is possible to express piecewise-continuous functions.  The semantics are as in a case statement: if cond_1 is true then f_1, else if cond_2 is true then f_2, and so on. f_otherwise gives a default case which corresponds to all conditions being false.  The default for f_otherwise is 0.

so, when I try to define the function on above command as:

f:=x->piecewise(x<0,x^2-2x+1,x>0,1-x)

f(0) = 0.