The Flying Colours Maths blog has been running posts twice weekly since 2012, covering maths from the basics to… well, the most advanced stuff I have a clue about.
Here they all are, sorted by date. Some day, other ways to filter them will be possible.
Dear Uncle Colin, I have a triangle. All I know is that its angles, $\alpha$, $\beta$ and $\gamma$, satisfy $\cos(\alpha)=\frac{1}{4}$ and $\gamma = 30º$ - and I have to find $\tan(\beta)$. Help! - Can’t Obviously See It, Need Explanation Hi, COSINE, and thanks for your message! This is one …
Sue de Pomerai joins Colin and Dave for this month’s episode of Wrong, But Useful. We discuss: Her work for FMSP and MEI and, previously as a teacher Sue’s alter ego, Ada Lovelace, and getting more young women into maths Colin writes books: he mentions Cracking Mathematics and some good …
Once upon a time1, @dragon_dodo asked me to help with: $\int_{- \piby 2}^{\piby 2} \frac{1}{2007^x+1} \frac{\sin^{2008}(x)}{\sin^{2008}(x)+\cos^{2008}(x)} \dx$. Heaven - or the other place - only knows where she got that thing from. Where do you even begin? My usual approach when I don’t know …
Dear Uncle Colin, What on earth is “expected goals” and why is it supposed to be useful? - Just Enjoy Football FFS Hello, JEFF, and thanks for your message! The first part of your question is simple, although with some subtleties. What does ’expected goals’ mean? …
You want to know one of my favourite things about maths? It’s the connections. Connections between things that don’t, on the face of it, seem remotely connected. One just cropped up, and made me grin from ear to ear, so I thought I’d share it with you. The Parker Square One of …
Dear Uncle Colin, Can you help me win the lottery using MATHS!? - Lots Of Time, Tremendous Optimism No. I mean, there’s a chapter in The Maths Behind1 on exactly that topic, but honestly? If I knew how to win the lottery, I’d be drinking mocktails on a Caribbean beach rather than writing …
A charming little puzzle from Brilliant: $x^2 + xy = 20$ $y^2 + xy = 30$ Find $xy$. I like this in part because there are many ways to solve it, and none of them the ‘standard’ way for dealing with simultaneous equations. You might look at it and say “Ah, there’s an $xy$ in …
Dear Uncle Colin, I’ve been set an evil integral: $\int_0^\piby{4} \frac{\sqrt{3}}{2 + \sin(2x)}\d x$. There is a hint to use the substitution $\tan(x) = \frac{1}{2}\left( -1 + \sqrt{3}\tan(\theta)\right)$, but I can’t see how that helps in the slightest. -- Let’s Integrate …
Some time back in the olden days, @robeastaway posted this: Before I say anything else: I do not consider this a useful question for 11-year-olds or anyone else. I particularly dislike that a method is mandated - long division is a fine algorithm, but I don’t think it’s appropriate to …
Dear Uncle Colin, I’m revising for a high-stakes exam. I learn material, do the exercises and think I understand it - but when I revisit it a couple of weeks later, it feels like I’m starting from scratch. What can I do to remember things better? -- Failure Of Remembering General Exam …
This month’s episode is the 2017 MathsJam special. What we talked about: Some tables Some talks we liked (featuring @reflectivemaths, @ajk_44, @zoelgriffifths (of whom more later), @macaronique, @chalkdustmag, @pecnut, @mscroggs, @televisionduck, Andrew Russell) Dave talks to @pecnut about his …
Before I begin: this post involves a puzzle and my attempt at a solution; everything above the horizontal rule is spoiler-free, but go beyond that at your peril. Some days, you can almost hear @colinthemathmo’s chuckle as he innocently poses a question such as: Find all configurations of 4 …
Dear Uncle Colin, When evaluating an expression, after you’ve dealt with brackets, powers and roots, do you deal with multiplication and division left to right, or does multiplication take precedence? - BIDMAS Idiocy Doesn’t Make Any Sense Hi, BIDMAS, and thanks for your message! There …
Recently, @solvemymaths asked the rather leading question: As with pretty much all mathematical notation questions, I have exactly one answer: for clarity. If it’s clearer to use the obelus than a fraction - a vinculum, if that’s your cup of magic potion - then you should use it. But …
Dear Uncle Colin I have a conceptual problem with impulse. Suppose you have a collision where your particle (of mass 1 kg) has an approach speed of 4m/s, changes direction, and leaves with a speed of 3m/s. That’s an impulse of -7 units, and the ball slows down from 4m/s to 3m/s. Suppose you …
The square root of 2 is 1.41421356237… Multiply this successively by 1, by 2, by 3, and so on, writing down each result without its fractional part: 1 2 4 5 7 8 9 11 12... Beneath this, make a list of the numbers that are missing from the first sequence: 3 6 10 13 17 20 23 27 30... The …
Dear Uncle Colin How does $\sqrt{9 - \sqrt{17}} = \frac{\sqrt{34}-\sqrt{2}}{2}$? I tried applying a formula, but I couldn’t make it work. - Roots Are Dangerous, It’s Chaotic A-Level Simplification Hi, RADICALS, and thank you for your message! Square roots of square roots are not usually …
In this month’s episode of Wrong, But Useful, Colin and Dave are joined by Special Guest Co-Host @pecnut, who is Adam Townsend in real life. Adam studies the behaviour of sperm in mucus, and chocolate fountains1 - when he’s not editing @chalkdustmag - Issue 6 of which is available now …
This puzzle was in February’s MathsJam Shout, contributed by the Antwerp MathsJam. Visit mathsjam.com to find your nearest event! Consider the set ${1, 11, 111, …}$ with 2017 elements. Show that at least one of the elements is a multiple of 2017. The Shout describes this one as tough; …
Dear Uncle Colin I’m stuck on a trigonometry proof: I need to show that $\cosec(x) - \sin(x) \ge 0$ for $0 < x < \pi$. How would you go about it? - Coming Out Short of Expected Conclusion Hi, COSEC, and thank you for your message! As is so often the case, there are several ways to …
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 of sides on each shape (e.g., …
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 looks at …
What’s that, @pickover? Shiver in ecstasy, you say? Just for a change. That’s neat. But why? Let’s suppose the circles all have radius 1, without loss of generality. Then the triangle’s side lengths are (in decreasing order) $2\sin\left( \piby 5 \right)$, $2\sin\left( \piby 6 …
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 set up …
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 has $a=2$, $b=1$ and $c=4$, …
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 Hi, TANGENT, and thanks for your message! For …
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 …
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 …
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 …
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 …