Hi all. Thank you for all the help, in particular Georgios Kokovidis's suggestion (with the link).
There were a couple of problems I encountered. The plot went beautifully.
However, when I tried exporting the graph to an eps file so that I can include it in my LaTeX file, 2 problems arises after latexing the file and "pdfing" it. One, the file was rotated anticlockwise by 90 degrees. Second, where I had -2Pi and -3Pi/2 plotted in Maple 12, the negative signs became "plus and minus" signs in the PDF file generated from LaTeX (the plus and minus signs I am referring to if you use LaTeX is \pm.).
I am puzzled!
Here is the code for Maple 12:
> with(plots):
> p1:=plot(sin(x),x=-2*Pi...2*Pi,tickmarks=[0,0],color=black):
> p2 := textplot([[Pi,-0.05,`p`], [Pi/2,-0.05,`p/2`],[-Pi/2,-0.05,`-p/2`], [-Pi,-0.05,`-p`],[0.2,-0.05,`0`],[-3*Pi/2,-0.05,`-3p/2`],[-2*Pi,-0.05,`-2p`],[3*Pi/2,-0.05,`3p/2`],[2*Pi,-0.05,`2p`]], align=below, font=[SYMBOL,10]):
> p3 := textplot([[-0.1,1.0,`1`], [-0.1,-1.0,`-1`],[-0.1,0.5,`y`],[2*Pi+1.5,-0.05,`x`]], align=left):
> p4:= pointplot ([[-Pi,0], [-Pi/2,0], [Pi/2,0],
[Pi,0],[0,1.0],[0,-1.0],[-3*Pi/2,0],[-2*Pi,0],[3*Pi/2,0],[2*Pi,0]], symbol=CROSS):
> display({p1,p2,p3,p4});
Another problem was when I tried using textplot, for example,
> p1:=textplot([[4*Pi/3+1,1,`y=2cos(x/2-Pi/6)`],[Pi-0.5,-1,`y=2cos (x/2)`]]):
the output was that the Pi within the quotation mark y=2cos(x/2-Pi/6) remains as Pi and not as a symbolic pi.
How do I overcome this?
Thanks.

Hi all. Thank you for all the help, in particular Georgios Kokovidis's suggestion (with the link).
There were a couple of problems I encountered. The plot went beautifully.
However, when I tried exporting the graph to an eps file so that I can include it in my LaTeX file, 2 problems arises after latexing the file and "pdfing" it. One, the file was rotated anticlockwise by 90 degrees. Second, where I had -2Pi and -3Pi/2 plotted in Maple 12, the negative signs became "plus and minus" signs in the PDF file generated from LaTeX (the plus and minus signs I am referring to if you use LaTeX is \pm.).
I am puzzled!
Here is the code for Maple 12:
> with(plots):
> p1:=plot(sin(x),x=-2*Pi...2*Pi,tickmarks=[0,0],color=black):
> p2 := textplot([[Pi,-0.05,`p`], [Pi/2,-0.05,`p/2`],[-Pi/2,-0.05,`-p/2`], [-Pi,-0.05,`-p`],[0.2,-0.05,`0`],[-3*Pi/2,-0.05,`-3p/2`],[-2*Pi,-0.05,`-2p`],[3*Pi/2,-0.05,`3p/2`],[2*Pi,-0.05,`2p`]], align=below, font=[SYMBOL,10]):
> p3 := textplot([[-0.1,1.0,`1`], [-0.1,-1.0,`-1`],[-0.1,0.5,`y`],[2*Pi+1.5,-0.05,`x`]], align=left):
> p4:= pointplot ([[-Pi,0], [-Pi/2,0], [Pi/2,0],
[Pi,0],[0,1.0],[0,-1.0],[-3*Pi/2,0],[-2*Pi,0],[3*Pi/2,0],[2*Pi,0]], symbol=CROSS):
> display({p1,p2,p3,p4});
Another problem was when I tried using textplot, for example,
> p1:=textplot([[4*Pi/3+1,1,`y=2cos(x/2-Pi/6)`],[Pi-0.5,-1,`y=2cos (x/2)`]]):
the output was that the Pi within the quotation mark y=2cos(x/2-Pi/6) remains as Pi and not as a symbolic pi.
How do I overcome this?
Thanks.