## In the mirror

I saw my face in the mirror, in passing, and it was someone else. I didn’t recognize the eyes, or the hair, or the point of the nose. But that wasn’...

## 0.999… = 1 and Zeno’s Paradox

Overview One surprisingly difficult concept for many students of mathematics is understanding that 0.999… (more properly depicted as $$0.9\overline{9}$$),...

## Negative numbers squared

Background Mathematical conventions represent the linguistic aspect of mathematics. One of the strengths of modern mathematics is the way in which we can repres...

## 10101 and 11011 are never prime

One particularly tricky aspect of number sense is being able to separate the abstract notion of value from more concrete visual representations of numbers, and ...

## Just forget my Dear Aunt Sally

The purpose of a mnemonic is to make something easier to remember. Roy G. Biv represents the major colors of the spectrum (Red, Orange, Yellow, Green, Blue, Ind...

## Multiplying Polynomials

The traditional way of teaching the multiplication of binomials is FOIL: First, Outside, Inside, Last. For instance: \[(x + 3)(2x – 5) = (x)(2x) + (x)(-5)...

## Hero’s Formula and Mirror Triangles

Here’s a problem with an interesting solution. You’re given two triangles, T1 and T2. The sides of T1 are 25, 25, and 30. The sides of T2 are 25, 25...