Mathematica Asked by Aharon Naiman on April 28, 2021
I am trying to show general cases of symmetry of regions.
However, for the following, Reduce
does not finish:
Reduce[ForAll[x,
x > 0, ! (RegionMember[ImplicitRegion[(0 < x < 1 || -2 < x < 0 || 2 < x < 3), {x}], {x}] [Xor]
RegionMember[ImplicitRegion[(0 < x < 1 || -2 < x < 0 || 2 < x < 3), {x}], {-x}])],
x, Reals]
OTOH, if I remove any one of the three conditions (from both parts), e.g.:
Reduce[ForAll[x,
x > 0, ! (RegionMember[ImplicitRegion[(-2 < x < 0 || 2 < x < 3), {x}], {x}] [Xor]
RegionMember[ImplicitRegion[(-2 < x < 0 || 2 < x < 3), {x}], {-x}])],
x, Reals]
it return False
immediately.
What’s happening?
(I know there are other ways to do this, e.g., with FindInstance
.)
Thanx.
Maybe other way.
reg1 = ImplicitRegion[(0 < x < 1 || -2 < x < 0 || 2 < x < 3), {x}]
reg2 = ImplicitRegion[(0 < x < 1 || -2 < x < 0 || 2 < x < 3) /.
x -> -x, {x}]
RegionEqual[reg1, reg2]
False
Correct answer by cvgmt on April 28, 2021
There is a workaround:
Reduce[ForAll[x, x > 0, ! (RegionMember[
ImplicitRegion[(0 < x < 1 || -2 < x < 0 ||
2 < x < 3), {x}], {x}] [Xor]
RegionMember[
ImplicitRegion[(0 < x < 1 || -2 < x < 0 ||
2 < x < 3), {x}], {-x}]) // Simplify], x, Reals]
(*False*)
Answered by user64494 on April 28, 2021
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