@vv I know your solution. I mean, it is not isomorphic. It is totally equal to each other. Can maple recognize that two groups are exactly equal? For example, g1 and g2 are not only isomorphic but exactly equal in the following:

g1 := PermutationGroup(Generators(SmallGroup(48, 8)));
g2 := PermutationGroup(NonRedundantGenerators(SmallGroup(48, 8)));

I want to select the exactly equal C₆ from SubgroupLattice(Symm(5), output=list). Is it possible?

@vv My this code return false all:

is(SubgroupLattice(S5, output = list)[i] = CyclicGroup(6)) $ (i = 1 .. 156)

Or maybe I cannot use false here to check it?

@vv Oh, this answer is solve my problem exactly. But could you explain what is convert~? I cannot search it in the help documentation.

@vv It's not PermutationGroup form still...I hope to get PermutationGroup({[[...]], [[...], [...]]}) form(even without those Perm). Then I can copy it into other software directly.

@vv I'm a newbie, how to use SubgroupLattice to detect the subgroup C₆ in S₅?

@vv If I use Wolfram Mathematica(similar to Maple) I will get this:

@vv Hello, thanks for your concern. But I note the documentation of Subgroup has no the usage of []. I just can find they use {}. How did you come up with the idea of using it?

@dharr Oh, god. I'm a Mathematica user. sorry for my this typo. Or I have to delete this post? Do you mind?

@vv 

I am not good at maple, but as your code, I even cannot calculate a are of a circle:

f:=x^(2)+y^(2)-1; 
F:=piecewise(f<0, 1, 0)
int(F, x = -2..2, y = -2..2)

I will get an error information

@Kitonum Is possible to get a closed-form solution by MultiInt?