@Markiyan Hirnyk 

@H-R   Obviously this is a typo. Instead of  plot/options  should be  plots[arrow] .

Only here instead of  width  the option  thickness  works.

@H-R  Just open the help on  Student[VectorCalculus][TangentVector]  command and everything is there.

@Axel Vogt 

Student[VectorCalculus][TangentVector](<cos(t), sin(t)>, range = 0 .. 2*Pi, curveoptions = [color = blue, thickness = 3], output = plot, scaling = constrained,vectors=10,vectoroptions = [shape=arrow, thickness = 3, color=red, length= 0.01, head_length = 1/16, head_width=1/16]);

@vv  But it's easy to fix

p:=3.5*x^2+3.2*x-6.5+88.3*x*y-y^3+a*y + sin(1);

evalindets(evalf(p), float, round);

@asa12  Replace the line  add(zip(`*`, c, [t]));   by  add(i, i = zip(`*`, c, [t]));  

or   `+`(op(zip(`*`, c, [t])));

@Markiyan Hirnyk  for a workaround. But the reasons of bugs in  solve  command are still not clear.

@Markiyan Hirnyk  Maybe you have in mind the following expression

Expr:=expand((x^2-x-3)^10)-exp(-x);

Find all minuses in it and their number, you can, for example, by conversion to string

convert(Expr, string);

StringTools[SearchAll]("-", %);  # positions of all the minus signs

nops([%]);  # total number of minuses  

Here is an another kind of animation. It uses a circular symmetry of the surface and of course much easier to implement than acer's method.

restart;

A := r->plot3d([2*cos(phi), 2*sin(phi), z], z = 0 .. 5, phi = 0 .. r, style = surface):

B :=r->plot3d([8*cos(phi), 8*sin(phi), z], z = 10 .. 20, phi = 0 .. r, style = surface):

C := r->plot3d([(-4+(6/5)*z)*cos(phi), (-4+(6/5)*z)*sin(phi), z], z = 5 .. 10, phi = 0 .. r, style = surface):

plots[animate](plots[display], ['A'(r), 'B'(r), 'C'(r), axes = normal, scaling = constrained], r = 0 .. 2*Pi, frames = 60, lightmodel = light4);

@hossayni  If you want to build multiple plots in one place, then there is no need to use  plots[display] . Just use a list of these plots. Here are 51 plots of  sin(m*x) , m=1..2  with the step  0.02

plot([seq(sin(m*x), m = 1 .. 2, 0.02)], x=0..2, color=green, thickness=2, axes=normal);

@nMaple  In the loop, you should assign names to these plots, and then (outside the loop)  build everything by  plots[display] command:

for i from 1 to 5 do

P[i]:=plot3d( ... ):

end do:

plots[display](seq(P[i], i=1..5));

@nMaple 

1) See help   on  readdata  command.

2) I did not understand - what  kind  of animation do you want?

@nMaple  All surfaces in my code defined by parametric equations, in which polar coordinates  r  and  phi  was actually used.  r(z)=2+6*((z-5)*(1/5))  is the equation of the line  through the 2 points  (5,2)  and  (10,8)

@Markiyan Hirnyk  Here are the basic steps in my code:

1) First, we specify the list  Lines  of 4 lines and the set  Points1  of 22 points (2 points for each domain).

2) Next we find the set  Packs  of all 4-points subsets of  Points1.

3) Next in a for loop, we choose such  sets of  Packs  that satisfies the condition (2 points on each side of any of the four lines). We get the set  Teams .

4) Using  ListTools[Categorize]  command  we divide the  set  Teams into equivalence classes on the basis:: two elements of  Teams  belong to the same class if the points of them lie in the same domains.

5) From each class choose one (first) element. We got the final result  Confs .

@sunflower  You can not write p[i]  because it  (i - the variable of the loop)  is not the  i-th prime number.