So you want to plot a function of x...  Here's one way to do it.
First you define the function.  Then, once you've defined the function
you plot it.
> f := x -> cos(x^(1/3));

                                       (1/3)
                        f := x -> cos(x     )

> plot(f(x),x=0..200);

             ** imagine seeing a figure right here **

Here's a second way to plot the function... you just type the function
into the plotting command...
> plot(cos(x^(1/3)),x=0..200);

             ** imagine seeing a figure right here **

So you want to plot a parametrized curve.  In this case it's an
ellipse.  Not that you could tell, the way maple plots it... maple
makes it look like a circle.  But the axes have different scales, if
you look closely.
> plot([3*cos(t),4*sin(t),t=0..2*Pi]);

             ** imagine seeing a figure right here **

Here's how to plot _two_ parametrized curves at once.  (oooooh!  and
you can plot three and four and...)
> plot({[3*cos(t),4*sin(t),t=0..2*Pi],[8*cos(t),4*sin(t),t=0..2*Pi]});

             ** imagine seeing a figure right here **

What if you want to plot the points that satisfy an equation, like x^2
+ y^2 = 1?  First, you have to give the command "with(plots):".  Once
you've done that, you can use the command "implicitplot".  (Note, if
you don't do the "with(plots)" first then maple won't know what you
mean by "implicitplot".  with(plots) introduces new commands to maple.
> with(plots):
Here we plot a circle.  Note how it looks like a circle. ;-)
> implicitplot(x^2+y^2=1,x=-2..2,y=-2..2);

             ** imagine seeing a figure right here **

Here's how to plot the solutions of two different equations.  In this
case we get a circle and a hyperbola.
> implicitplot({x^2+y^2=1,x^2-y^2=3},x=-4..4,y=-4..4);

             ** imagine seeing a figure right here **