Obviously, that  f:=x->x^3  is the same function as  g:=t->t^3 . But

f:= x-> x^3;  g:= t-> t^3;

is(f=g);

Worse yet

f:= x-> x^3;  g:= x-> x^3;

is(f=g);

Is there some sort of analog of  option  discont=true  in  plot3d?  Can I remove these vertical cylindrical surfaces in the following example? They correspond to the zeros of the denominator:

plot3d((x^2+sin(x))/(y^2+cos(x)), x = -7 .. 7, y = -5 .. 5, view = [-7 .. 7, -6 .. 6, -1 .. 7], numpoints = 50000, scaling = constrained, axes = normal);

plots[implicitplot](y^2+cos(x), x = -7 .. 7, y = -5 .. 5, scaling = constrained, numpoints = 5000);

Is it possible to use Unicode characters in  textplot  command? In the application that I'm developing, the signs of the chess pieces should be used.

Two examples:

for i in {1, 2/0, -3, 1/4, 5} do

if i::posint then print(i)  fi;

od;

       Error, numeric exception: division by zero

select(x->is(x::posint), {1, 2/0, -3, 1/4, 5});

       Error, numeric exception: division by zero

How to avoid interruption of the program in such cases?

My attempt:

RealDomain[solve]({x^2+y^2+z^2 = 3, x+y+z = 3}, {x,y,z});

             {x = -RootOf(_Z^2+(z-3)*_Z+z^2-3*z+3)-z+3, y = RootOf(_Z^2+(z-3)*_Z+z^2-3*z+3), z = z}

In fact, the system in the real domain has a unique solution x = 1, y = 1, z = 1. It is easy to find by hand, noting that the plane  x + y + z = 3  is tangent to the sphere