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Zduff
  • Member for 8 years, 6 months
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71 votes
12 answers
12k views

Why do we not have to prove definitions?

19 votes
3 answers
2k views

Why do PDE's seem so unnatural? [closed]

12 votes
4 answers
43k views

Prove distributive law of sets

8 votes
2 answers
1k views

Why can I make the substitution $x = \sin \theta$?

8 votes
3 answers
3k views

If $|x_{n+1} - x_n| < \epsilon,$ is $(x_n) $ a Cauchy sequence?

7 votes
4 answers
11k views

Why can't length be negative?

7 votes
2 answers
129 views

Is it valid to define $\binom{n}{n+k} = 0$

6 votes
2 answers
402 views

Show $f(x) = 1/x$ is in $L^2\left([1, +\infty)\right)$ but not in $L^1\left([1, +\infty)\right)$.

6 votes
1 answer
4k views

Prove $\frac{1}{x^2}$ is uniformly continuous on $[1,\infty)$ but not on $(0,1)$.

5 votes
4 answers
1k views

Equality/Equivalence of functions

5 votes
2 answers
2k views

What is the physical interpretation of homogeneous?

5 votes
3 answers
335 views

Particular definition of e

5 votes
0 answers
192 views

Prove that $\lim_{n \to \infty} \int_{[0,1]}{x^n}\, dx = 0$. Where $\int$ represents Lebesgue integration.

5 votes
1 answer
701 views

In a Hilbert space $x_n \overset{\text{w}}{\to} x$ and $y_n \to y$. Prove $\langle x_n, y_n \rangle \to \langle x, y \rangle$

4 votes
2 answers
2k views

Find all metrics on a set $X$ consisting of two points. Consisting of one point.

4 votes
3 answers
4k views

Rank one orthogonal projector matrix.

4 votes
1 answer
381 views

Forcing zero entries with unitary matrix operations.

4 votes
0 answers
2k views

Prove the Cantor set has no interior.

4 votes
2 answers
119 views

Is this limit dependent on x. Derivative natural log.

4 votes
2 answers
1k views

Ending a proof with "the result follows".

4 votes
3 answers
11k views

Why change the sign of the integral when switching the limits of integration?

4 votes
0 answers
632 views

Why is cos at $\pi/2$ not undefined?

4 votes
3 answers
141 views

Prove $f(x) = \frac{1}{1+x^2}$ is uniformly continuous on $\mathbb{R}$

3 votes
0 answers
68 views

Proof of this pattern in the root 2 algorithm.

3 votes
1 answer
2k views

How does a uniform distribution have a mean?

3 votes
0 answers
269 views

What is a test function and why do we need them?

3 votes
1 answer
70 views

Can I manipulate a function (with a parameter) to show it converges to another function?

3 votes
0 answers
75 views

If $L^*$ is the formal self-adjoint of and $n$th order differential operator $L$ show that the formal adjoint of $L^*$ is $L$.

3 votes
1 answer
745 views

Parallelogram Law Geometric Proof

3 votes
4 answers
258 views

For $\langle Tx, x \rangle \geq \|x\|^2$, prove a solution exists for $Tx = y$.

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