# The Flying Colours Maths Blog: Latest posts

## Tessellations and cuboids

On a recent1 episode of Wrong, But Useful, Dave mentioned something interesting2: if you take three regular shapes that meet neatly at a point – for example, three hexagons, or a square and two octagons – and make a cuboid whose edges are in the same ratio as the number

## Ask Uncle Colin: Simultaneous Trigonometry

Dear Uncle Colin, I'm normally pretty good at simultaneous equations, but I can't figure out how to solve this for $a$ and $b$. $\cos(a)-\cos(b) = x$ $\sin(a)-\sin(b) = y$ – Any Random Circle Hi, ARC, and thanks for your message! This is, it turns out, a bit trickier than it

## Are you sure that’s a right angle?

What's that, @pickover? Shiver in ecstasy, you say? Just for a change. Shiver in ecstasy. The sides of a pentagon, hexagon, & decagon, inscribed in congruent circles, form [a] right triangle. pic.twitter.com/Uastgc7SJo — Cliff Pickover (@pickover) May 20, 2017 That's neat. But why? Let's suppose the circles all have radius

## Ask Uncle Colin: Shouldn’t this be simple?

Dear Uncle Colin, I've got a funny square and I can't find $x$. Can you help? – Oughta Be Simple, Can't Unravel Resulting Equations Hi, OBSCURE, and thanks for your message! You're right, it ought to be simple… but it turns out not to be. It is simple enough to

## Lines and squares

This puzzle presumably came to me by way of @ajk44, some time ago. Thanks, Alison! The problem, given here, is to find the equations of two lines that complete a square, given: Two of the lines are $y=ax+b$ and $y=ax+c$ One of the vertices is at $(0,b)$. The example given

## Ask Uncle Colin: touching cubics

Dear Uncle Colin, I'm told that the graphs of the functions $f(x) = x^3 + (a+b)x^2 + 3x – 4$ and $g(x) = (x-3)^3 + 1$ touch, and I have to determine $a$ in terms of $b$. Where would I even start? – Touching A New Graph Except Numerically Troubling

## Revisiting Basel

Some while ago, I showed a slightly dicey proof of the Basel Problem identity, $\sum_{n=1}^{\infty} \frac{1}{n^2} = \frac {\pi^2}{6}$, and invited readers to share other proofs with me. My old friend Jean Reinaud stepped up to the mark with an exercise from his undergraduate textbook: The French isn't that difficult,

## Ask Uncle Colin: An Infinite Sum

Dear Uncle Colin I've been asked to find $\sum_3^\infty \frac{1}{n^2-4}$. Obviously, I can split that into partial fractions, but then I get two series that diverge! What do I do? – Which Absolute Losers Like Infinite Series? Hi, WALLIS, and thanks for your message! Hey! I'm an absolute loser who

## Wrong, But Useful: Episode 48

In this month's episode of Wrong, But Useful, Colin and Dave are joined by @niveknosdunk, who is Professor Kevin Knudson in real life. Kevin, along with previous Special Guest Co-Host @evelynjlamb, has recently launched a podcast, My Favorite Theorem The number of the podcast is 12; Kevin introduces us to

## The Paradox of the Second Ace

This post is inspired by a Futility Closet article. Do visit them and subscribe to their excellent podcast! Suppose you're dealt a bridge hand1, and someone asks whether you have any aces; you check, and yes! you find an ace. What's the probability you have more than one ace? This