User Chris - Mathematics Stack Exchange

15 votes

Rigorous nature of combinatorics

answered Jun 14, 2017 at 2:29

14 votes

Accepted

Straightedge-only construction of a perpendicular

answered Sep 1, 2013 at 4:54

9 votes

Verifying a proof that if $x,y,z \geq 0$ and $x+y+z = 1$, then $0 \le xy + yz + zx - 2xyz \le \frac{7}{27}$

answered Apr 27, 2013 at 22:09

9 votes

How to find $\lim_{n\to\infty}\frac{1!+2!+\cdots+n!}{n!}$?

answered Sep 8, 2013 at 7:17

6 votes

If a number is rational, then it has a periodic decimal expression?

answered Jul 6, 2017 at 4:08

5 votes

Accepted

Construction of the real numbers using Dedekind cuts

answered Jan 9, 2018 at 4:11

5 votes

Proof the set $\mathbb{Z}_p$ is a field

answered Mar 3, 2017 at 5:57

5 votes

Accepted

How closely packed can the points of a compact metric space be?

answered Jan 25, 2017 at 16:31

4 votes

prove combinatorics theorem

answered Mar 2, 2017 at 4:34

4 votes

Accepted

Prove or disprove my conjecture about triangles.

answered Jan 24, 2017 at 9:16

4 votes

Accepted

These two sequences have the same limit

answered Aug 20, 2013 at 5:36

4 votes

Accepted

Finding a function (?) and computing its definite integral

answered Sep 29, 2015 at 0:50

3 votes

Limit of $\frac{x^{x^x}}{x}$ as $x\to 0^+$

answered Jun 5, 2012 at 9:20

3 votes

Maximum of $a_1 \cdot a_2 \cdots a_n$ given $a_1 + \cdots + a_n = 1000$?

answered Mar 4, 2017 at 17:19

3 votes

How can I advance?

answered Jul 19, 2017 at 18:28

3 votes

Why is a strictly monotonic mapping between intervals continuous?

answered Jun 25, 2017 at 0:44

3 votes

Prove that if $(f_n)$ converges to $f$ in measure then $(f_n^2)$ converges to $f^2$ in measure.

answered Jun 25, 2017 at 21:57

3 votes

Accepted

Bernoulli polynomials identity

answered Jul 2, 2017 at 21:29

2 votes

Accepted

How can I prove that the GCD is less or equal than the square root of the numbers' sum?

answered Jun 19, 2017 at 20:25

2 votes

Maclaurin expansion of zero

answered Jul 30, 2017 at 2:55

2 votes

Prob. 7 (b), Chap. 6, in Baby Rudin: Example of a function such that $\lim_{c \to 0+} \int_c^1 f(x) \ \mathrm{d}x$ exists but . . .

answered Jul 30, 2017 at 20:47

2 votes

Struggling to understand derivative

answered Jul 17, 2017 at 6:47

2 votes

Accepted

Unions of Sets of Limit Points

answered Sep 27, 2017 at 1:53

2 votes

Prove that $p^4 - 1$ is divisible by by $120$.

answered Oct 13, 2017 at 5:59

2 votes

Accepted

Prove recurrent formula $(n+2)\int_{0}^{\pi} \ln{(\sin{\frac{x}{2}})}\cos{(n+2)x}dx = n\int_{0}^{\pi} \ln{(\sin{\frac{x}{2}})}\cos{nx}dx$

answered May 27, 2017 at 19:41

2 votes

Accepted

How to do this induction proof?

answered Jan 28, 2017 at 21:12

2 votes

Accepted

Limit of integrals using the dominated convergence theorem

answered Feb 12, 2017 at 14:56

2 votes

Proving a function is a metric

answered Sep 29, 2015 at 0:08

2 votes

Accepted

Infinite series converges to 1 proof

answered Jan 18, 2017 at 21:29

2 votes

Proving that $\alpha^{n-2}\leq F_n\leq \alpha^{n-1}$ for all $n\geq 1$, where $\alpha$ is the golden ratio

answered Jan 3, 2013 at 3:18

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60 Answers

Rigorous nature of combinatorics

Straightedge-only construction of a perpendicular

Verifying a proof that if $x,y,z \geq 0$ and $x+y+z = 1$, then $0 \le xy + yz + zx - 2xyz \le \frac{7}{27}$

How to find $\lim_{n\to\infty}\frac{1!+2!+\cdots+n!}{n!}$?

If a number is rational, then it has a periodic decimal expression?

Construction of the real numbers using Dedekind cuts

Proof the set $\mathbb{Z}_p$ is a field

How closely packed can the points of a compact metric space be?

prove combinatorics theorem

Prove or disprove my conjecture about triangles.

These two sequences have the same limit

Finding a function (?) and computing its definite integral

Limit of $\frac{x^{x^x}}{x}$ as $x\to 0^+$

Maximum of $a_1 \cdot a_2 \cdots a_n$ given $a_1 + \cdots + a_n = 1000$?

How can I advance?

Why is a strictly monotonic mapping between intervals continuous?

Prove that if $(f_n)$ converges to $f$ in measure then $(f_n^2)$ converges to $f^2$ in measure.

Bernoulli polynomials identity

How can I prove that the GCD is less or equal than the square root of the numbers' sum?

Maclaurin expansion of zero

Prob. 7 (b), Chap. 6, in Baby Rudin: Example of a function such that $\lim_{c \to 0+} \int_c^1 f(x) \ \mathrm{d}x$ exists but . . .

Struggling to understand derivative

Unions of Sets of Limit Points

Prove that $p^4 - 1$ is divisible by by $120$.

Prove recurrent formula $(n+2)\int_{0}^{\pi} \ln{(\sin{\frac{x}{2}})}\cos{(n+2)x}dx = n\int_{0}^{\pi} \ln{(\sin{\frac{x}{2}})}\cos{nx}dx$

How to do this induction proof?

Limit of integrals using the dominated convergence theorem

Proving a function is a metric

Infinite series converges to 1 proof

Proving that $\alpha^{n-2}\leq F_n\leq \alpha^{n-1}$ for all $n\geq 1$, where $\alpha$ is the golden ratio