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For questions in Mathematics Education as a scientific discipline. For more hands-on questions on teaching Mathematics, please use the tag teaching. There is also a Stack Exchange community http://matheducators.stackexchange.com/

32 votes

Real-world applications of mathematics, by arxiv subject area?

math.CO Combinatorics Combinatorics finds applications in computer science, especially in the run-time analysis of algorithms. It has also in recent years found applications in physics, at least in …
Martin Sleziak's user avatar
73 votes

Sophisticated treatments of topics in school mathematics

It's common in calculus classes and textbooks to state that the antiderivative of $\frac{1}{x}$ is $\log |x| + C$, where $C$ is a constant. This is incorrect: $C$ need only be a locally constant funct …
John Pardon's user avatar
  • 18.7k
86 votes

Sophisticated treatments of topics in school mathematics

The angle addition formula $\tan(\alpha + \beta) = \frac{\tan(\alpha) + \tan(\beta)}{1 - \tan(\alpha) \tan(\beta)}$ for tangent gives one of the simplest nontrivial examples of a formal group law, nam …
Qiaochu Yuan's user avatar
24 votes

Is Euclid dead?

As long as this question is open I might as well throw in my two cents. I think it is not useful to teach Euclidean geometry to high school students. Here are some reasons I can think of for people to …
Qiaochu Yuan's user avatar
38 votes

Are there proofs that you feel you did not "understand" for a long time?

The first proof of Tychonoff's theorem I learned, from the Alexander subbase theorem, was completely mysterious to me. I didn't understand it at all. In particular I didn't really understand what the …
Qiaochu Yuan's user avatar
3 votes

Seeking a Geometric Proof of a Generalized Alternating Series' Convergence

Here's an idea. Group the series into blocks $$\sum_{n=dk}^{d(k+1) - 1} \frac{z^n}{n}$$ where $d$ is fixed and large enough that the complex numbers $1, z, z^2, ... z^{d-1}$ are approximately unifor …
Qiaochu Yuan's user avatar
3 votes

Short Course Suggestions For High School Students

I think a course about homogeneous linear recurrence relations with constant coefficients should be manageable. The simplest nontrivial example is probably the Fibonacci recurrence $$F_{n+2} = F_{n+1} …
Qiaochu Yuan's user avatar
25 votes

Taylor's theorem and the symmetric group

One way is to use a combinatorial definition of the derivative. Let $A(z) = \sum a_n z^n$ be a power series. In combinatorics, where $A$ is likely to be an ordinary generating function, $a_n$ is likel …
Qiaochu Yuan's user avatar
115 votes

What are your favorite instructional counterexamples?

A polynomial $p(x) \in \mathbb{Z}[x]$ is irreducible if it is irreducible $\bmod l$ for some prime $l$. This is an important and useful enough sufficient criterion for irreducibility that one might w …
Chandan Singh Dalawat's user avatar
17 votes

Teaching undergraduate students to write proofs

Regarding different flavors of approach 1, here are some words from Halmos. I have taught courses whose entire content was problems solved by students (and then presented to the class). The number of …
Qiaochu Yuan's user avatar
32 votes

How to present mathematics to non-mathematicians?

There is this nice quote whose wording I can't quite recall. It is something like "physics is the study of the laws of God. Mathematics is the study of the laws even God must follow." I think there …
David Roberts's user avatar
  • 35.5k
5 votes

How do I explain the number e to a ten year old?

Here is one way which I learned from Clio Cresswell's Mathematics and Sex, although unfortunately I'm not sure how to prove it. Suppose you are sure that you will meet exactly $n$ suitable marriage p …
Qiaochu Yuan's user avatar
34 votes

Examples of common false beliefs in mathematics

The quotient $G/Z(G)$ of a group by its center is centerless. I definitely thought this until it was pointed out to me in a Lie theory textbook that this wasn't true in general, but is true for (edit …
Qiaochu Yuan's user avatar
3 votes

What are your experiences of handouts in mathematics lectures?

One basic observation, as a student. A big reason for providing notes is if the class works out of more than one textbook (or none at all!) and you want to keep the narrative straight. The professor …
Qiaochu Yuan's user avatar
278 votes

Examples of common false beliefs in mathematics

I don't know if this is common or not, but I spent a very long time believing that a group $G$ with a normal subgroup $N$ is always a semidirect product of $N$ and $G/N$. I don't think I was ever sho …
Qiaochu Yuan's user avatar

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