User Xander Henderson - Mathematics Stack Exchange

93 votes

Can area of rectangle be greater than the square of its diagonal?

answered Nov 15, 2018 at 19:01

75 votes

Accepted

Why do we need so many trigonometric definitions?

answered Mar 29, 2018 at 16:43

55 votes

"Gaps" or "holes" in rational number system

answered Apr 29, 2020 at 16:09

42 votes

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Why do I get a converging result when pressing cosine multiple times on a calculator?

answered Oct 11, 2017 at 19:24

33 votes

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What is the name of the number that is being added to another number?

answered May 20, 2018 at 23:18

32 votes

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A curiosity: how do we prove $\mathbb{R}$ is closed under addition and multiplication?

answered Dec 12, 2018 at 4:06

32 votes

Is the chain rule needed at all to solve this problem?

answered Feb 21, 2025 at 15:50

26 votes

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Do we care if term in sequence makes our step invalid when calculating a limit?

answered Jan 27 at 22:58

25 votes

Why is a derivative defined using limits?

answered Jun 27, 2018 at 2:44

25 votes

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What's the precise meaning of the expression "induced by" in mathematics?

answered Mar 23, 2018 at 15:15

25 votes

Accepted

Getting different answers when integrating using different techniques

answered Nov 27, 2019 at 18:50

24 votes

Let $A\subset\mathbb{R}$ be an uncountable set of irrational numbers. Does there exist a finite $B\subset A$ such that $\sum_{x\in B} x\in\mathbb{Q}?$

answered Jan 1, 2024 at 17:53

23 votes

How can I show a supremum of a set is also its limit point?

answered Dec 5, 2018 at 14:24

21 votes

Accepted

Why is the word "complement" used in set theory?

answered Aug 8, 2017 at 13:51

21 votes

What is a natural number?

answered Sep 20, 2017 at 19:26

19 votes

Accepted

Is linear independence of vectors transitive?

answered Sep 3, 2017 at 1:02

19 votes

Are one-by-one matrices equivalent to scalars?

answered Sep 9, 2018 at 20:40

19 votes

Accepted

An alternative proof that the reals are uncountably infinite.

answered Apr 9, 2025 at 0:11

18 votes

Example of a point that is not the limit of any sequence in a connected topological space

answered Feb 15, 2024 at 13:28

18 votes

Accepted

What is the meaning of the $c$ in $C_c^{\infty}(\mathbb{R})$?

answered Sep 20, 2019 at 17:02

17 votes

Accepted

Set theoretic difference $A-B$ contradicting $\emptyset \in B$?

answered Dec 25, 2017 at 18:33

16 votes

Accepted

Counter example for $\int_\mathbb{R} f_nd\mu\rightarrow\int_\mathbb{R} fd\mu$

answered Aug 9, 2017 at 21:35

16 votes

Implicit differentiation - why can you substitute the expression?

answered Mar 12, 2025 at 21:22

16 votes

Accepted

About the domain of the derivative

answered Jan 19, 2024 at 22:07

15 votes

A family has a child. They adopt a girl as well. If one of the children becomes #1 in a women's race, what is the probability it's the adopted girl?

answered Mar 24, 2025 at 20:54

15 votes

Speed of two trains travelling side by side

answered Jan 10, 2018 at 14:43

14 votes

Complement Set of Cartesian product

answered Sep 12, 2017 at 3:53

14 votes

Accepted

Is the product of all positive rational numbers equal to one?

answered Feb 18, 2018 at 17:27

14 votes

Where is the inconsistentency hiding in Langley's adventitious angle?

answered Jul 12, 2025 at 16:22

13 votes

Accepted

Is there a mathematical operator that will turn a matrix into its absolute values?

answered Nov 10, 2019 at 16:15

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799 Answers

Can area of rectangle be greater than the square of its diagonal?

Why do we need so many trigonometric definitions?

"Gaps" or "holes" in rational number system

Why do I get a converging result when pressing cosine multiple times on a calculator?

What is the name of the number that is being added to another number?

A curiosity: how do we prove $\mathbb{R}$ is closed under addition and multiplication?

Is the chain rule needed at all to solve this problem?

Do we care if term in sequence makes our step invalid when calculating a limit?

Why is a derivative defined using limits?

What's the precise meaning of the expression "induced by" in mathematics?

Getting different answers when integrating using different techniques

Let $A\subset\mathbb{R}$ be an uncountable set of irrational numbers. Does there exist a finite $B\subset A$ such that $\sum_{x\in B} x\in\mathbb{Q}?$

How can I show a supremum of a set is also its limit point?

Why is the word "complement" used in set theory?

What is a natural number?

Is linear independence of vectors transitive?

Are one-by-one matrices equivalent to scalars?

An alternative proof that the reals are uncountably infinite.

Example of a point that is not the limit of any sequence in a connected topological space

What is the meaning of the $c$ in $C_c^{\infty}(\mathbb{R})$?

Set theoretic difference $A-B$ contradicting $\emptyset \in B$?

Counter example for $\int_\mathbb{R} f_nd\mu\rightarrow\int_\mathbb{R} fd\mu$

Implicit differentiation - why can you substitute the expression?

About the domain of the derivative

A family has a child. They adopt a girl as well. If one of the children becomes #1 in a women's race, what is the probability it's the adopted girl?

Speed of two trains travelling side by side

Complement Set of Cartesian product

Is the product of all positive rational numbers equal to one?

Where is the inconsistentency hiding in Langley's adventitious angle?

Is there a mathematical operator that will turn a matrix into its absolute values?