Thank you, this is it. For anyone reading this to whom it would be useful: command for plotting the solid I wanted is:

plot3d([t-sin(t), sqrt((1-cos(t))^2)*cos(s), sqrt((1-cos(t))^2)*sin(s)], s = 0 .. 2*Pi, t = 0 .. 2*Pi, axes = frame, labels = ["x", "y", "z"]);

Thank you, this is it. For anyone reading this to whom it would be useful: command for plotting the solid I wanted is:

plot3d([t-sin(t), sqrt((1-cos(t))^2)*cos(s), sqrt((1-cos(t))^2)*sin(s)], s = 0 .. 2*Pi, t = 0 .. 2*Pi, axes = frame, labels = ["x", "y", "z"]);

@Robert Israel: Thank you, this is exactly what I wanted! Very nice.

@Robert Israel: Thank you, this is exactly what I wanted! Very nice.

@Oliver K  In my point of view (and I think I am not alone),

  and (x*(x^2-2*x))/(x^2-2*x) are equal and they both have discontiunity in x=2. 

I have found another "weakness" - discont command can not work with piecewise functions. You can try very simple example:  discont(piecewise(x <= 0, x, x >= 0, x), x);

@Oliver K  In my point of view (and I think I am not alone),

  and (x*(x^2-2*x))/(x^2-2*x) are equal and they both have discontiunity in x=2. 

I have found another "weakness" - discont command can not work with piecewise functions. You can try very simple example:  discont(piecewise(x <= 0, x, x >= 0, x), x);

One thing which I have in my mind right now is improving plots with removable discontinuities. It was a new functionality in Maple 14, but it doesn't work properly. Sometimes it shows the discontinuities, sometimes not. Just a few expamples:

plot(x*(x^2-2*x)*(1/(x^2-2*x)), x = -3 .. 3, discont = [showremovable]);
plot((x^3-2*x^2)*(1/(x^2-2*x)), x = -3 .. 3, discont = [showremovable]);

f:=x->(x-1)^3/(x^2-1):
plot(f,-5..5,-20..10,discont=[showremovable]);
plot(f(x),x=-5..5,y=-20..10,discont=[showremovable]);

Robert Israel is right, I was writing about a slider in a maplet. 

There has to be a solution, since you can see it in the Plot Builder when you try to plot for example the expression a*x where a is a parameter ranging from 0 to 1. But I do not know how it is done there.

Robert Israel is right, I was writing about a slider in a maplet. 

There has to be a solution, since you can see it in the Plot Builder when you try to plot for example the expression a*x where a is a parameter ranging from 0 to 1. But I do not know how it is done there.

Thank you,

it has not crossed my mind (that I can use "plots\interactive" command).

Thank you,

it has not crossed my mind (that I can use "plots\interactive" command).

Thank you for your reply, but I would like to see a source code of the whole Plot Builder as a maplet. 

Thank you for your reply, but I would like to see a source code of the whole Plot Builder as a maplet. 

Is there also possibility to view the source code of Plot Builder?

@hirnyk Do you mean to change units in the expression I deal with? That is a problem. With the maplet I would like to show a solution of the easiest population growth model, i.e. a solution of the equation

and I would like to plot it according to the value of "N(0)" and "r". In this case it is very useful to be able to work with "small" values of "r" and to use also decimal numbers. Therefore I would like to use for example a slider with minimum at "-1" and maximum at "1" and to show tickmarks with a step smaller than 1 whole unit.

There has to be some way to do it, since when you use Plot Builder and choose Interactive plot with a parameter, then you can see tickmarks with a step smaller than 1 whole unit. But I do not know how it is done in this Plot Builder.

This leads to another question: Is it possible to view the source codes of the maplets which are available in Maple? One of these maplets is this Plot Builder, but there are also many tutors etc.