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1d
comment Nowhere dense subset of unit square of measure $1$
@PhoemueX Well color me shocked. Measure theory makes my head hurt.
1d
comment Are there nonsmooth Lie groups?
Continuous meaning? Not-discrete?
1d
comment How many distanct equivalence classes are picked out by this relation?
What kind of numbers are $x$ and $y$?
1d
comment Proving two matrices are cogredient over $\mathbb{Q}$
I've edited my answer since I made a slight error. It's much clearer now.
1d
comment Why is $f'(c) = \text{does not exist}$ a critical point?
I think the use of critical here is in the sense that the derivative has a sign change. Consider $f(x) = \frac{1}{x^2}$. The derivative to the left of $0$ is positive and to the right of $0$ is negative.
1d
revised Proving two matrices are cogredient over $\mathbb{Q}$
added 340 characters in body
1d
answered Proving two matrices are cogredient over $\mathbb{Q}$
2d
answered period of $\cos(x) + x - \lfloor x \rfloor$?
2d
comment Differential equation $y''-4y = e^{-x}$
Have you tried using the formula in the variation of parameters method?
2d
answered Why is the constraint $\|w\| = 1$ non-convex?
2d
comment What's my mistake in this integral transformation?
@DanielS. I'm glad you understand it now :)
2d
comment Proof that $n\Bbb Z \leq \Bbb Z$ and are the only subgroups of $\Bbb Z$
@SalmonKiller You're exactly right.
2d
comment What's my mistake in this integral transformation?
@DanielS. In that case, $dz = 10 x\,dx$. You take the derivative of $z$ and get that $dz = z'(x)\,dx$.
2d
comment What's my mistake in this integral transformation?
@Bye_World That's another good observation!
2d
comment What's my mistake in this integral transformation?
Alternatively, you can compute the area using triangles if you are so inclined.
2d
comment What's my mistake in this integral transformation?
You missed the negative sign in his work. He didn't make the mistake when switching the bounds. It was just that he omitted $dz = -dx$.
2d
comment Proof that $n\Bbb Z \leq \Bbb Z$ and are the only subgroups of $\Bbb Z$
You can write $v = kn + r$. If $v\in H$ but $v$ isn't a multiple of $r$, note that $v - kn = r\in H$, right? Can you take it from there?
2d
comment Homeomorphism in the definition of a manifold
I think the word locally is meant to apply to both the manifold and Euclidean space so it's implied to some degree.
2d
comment Proof that $n\Bbb Z \leq \Bbb Z$ and are the only subgroups of $\Bbb Z$
@SalmonKiller You're on the right track. If you use the division algorithm, then what can you say about the remainder? How does this give a contradiction?
2d
answered What's my mistake in this integral transformation?