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Examples-counterexamples
New post in Examples-counterexamples
The range of the derivative of a differentiable function
November 17th, 2020
derivatives
real-analysis
examples-counterexamples
example of a subgroup of index $3$ which is not normal
August 1st, 2022
group-theory
abstract-algebra
normal-subgroups
examples-counterexamples
Looking for examples of first countable, compact spaces which is not separable
August 1st, 2022
general-topology
examples-counterexamples
are continuous functions that map measure zero sets to measure zero sets absolutely continuous?
August 1st, 2022
real-analysis
examples-counterexamples
Quotient of a locally compact space
June 23rd, 2020
quotient-spaces
general-topology
examples-counterexamples
Total Variation Measure: Definition?
August 1st, 2022
examples-counterexamples
sequences-and-series
measure-theory
If $g \circ f$ is surjective, show that $f$ does not have to be surjective?
September 22nd, 2020
elementary-set-theory
function-and-relation-composition
examples-counterexamples
functions
Diffeomorphisms: Examples and Importance
August 1st, 2022
differential-geometry
examples-counterexamples
Does a monotone function on an arbitrary subset of $\mathbb R$ always have at most countable number of discontinuity?
August 1st, 2022
examples-counterexamples
continuity
real-analysis
Quotient map that is not closed
August 1st, 2022
quotient-spaces
examples-counterexamples
algebraic-topology
general-topology
closed-map
Product of quotient maps and quotient space that is not Hausdorff
August 1st, 2022
general-topology
examples-counterexamples
Examples of contravariant functors
August 1st, 2022
category-theory
soft-question
big-list
examples-counterexamples
Example of a surjective local homeomorphism that is not a covering?
August 1st, 2022
examples-counterexamples
general-topology
covering-spaces
algebraic-topology
Is every Hilbert space an $L^2$ space?
August 1st, 2022
hilbert-spaces
examples-counterexamples
measure-theory
functional-analysis
An Example of a Torsion Module
June 15th, 2020
modules
examples-counterexamples
ring-theory
abstract-algebra
linear-algebra
Explaining roundoff error when row reducing matrices
March 10th, 2022
numerical-linear-algebra
linear-algebra
numerical-methods
examples-counterexamples
Example of a normal extension.
August 1st, 2022
field-theory
examples-counterexamples
extension-field
Middle cancellation in a group
August 1st, 2022
examples-counterexamples
group-theory
abstract-algebra
If squared series is convergent then series is convergent absolutely?
August 1st, 2022
sequences-and-series
examples-counterexamples
Counterexample for $(a*b)^2=a^2*b^2$
August 1st, 2022
abstract-algebra
group-theory
examples-counterexamples
Mixing and Distributing Qualifiers ($\forall x$, $\exists x$)
August 1st, 2022
logic
quantifiers
predicate-logic
examples-counterexamples
Examples of nowhere continuous functions
December 22nd, 2020
real-analysis
examples-counterexamples
The set of all equivalence classes of an equivalence relation on a uncountable set may be countable or uncountable.
August 1st, 2022
equivalence-relations
elementary-set-theory
examples-counterexamples
cardinals
Composition of functions is continuous?
August 1st, 2022
calculus
real-analysis
functions
continuity
examples-counterexamples
Give an example of a function that is bounded and continuous on the interval [0, 1) but not uniformly continuous on this interval.
August 1st, 2022
real-analysis
continuity
examples-counterexamples
uniform-continuity
Pointwise convergence of uniformly continuous functions to zero, but not uniformly
August 1st, 2022
uniform-convergence
uniform-continuity
real-analysis
pointwise-convergence
examples-counterexamples
Famous Finite Sets
December 8th, 2020
recreational-mathematics
examples-counterexamples
big-list
$3\times 3$ matrix with no real eigenvalues
August 1st, 2022
linear-algebra
matrices
eigenvalues-eigenvectors
examples-counterexamples
Concrete examples of group actions.
August 1st, 2022
group-actions
group-theory
examples-counterexamples
Draw a non-planar graph whose complement is a non-planar graph
August 1st, 2022
examples-counterexamples
graph-theory
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