Andrew Stacey
@mathforge.org
Mathematician: formerly academic (differential topology), currently educational (Head of Department in a UK secondary school).
Side interests in Maths & Programming & Art.
Website: https://loopspace.mathforge.org
Side interests in Maths & Programming & Art.
Website: https://loopspace.mathforge.org
Buying hot dogs today. The prices per 100g on the signs are a bit blurred, they were 27.7p per 100g for the jar of 12 and 43.4p per 100g for the jar of 6.
After staring at them for some time, and using a calculator to double check, I did buy the jar of 12 as it was the cheaper option.
#UKMathsChat
After staring at them for some time, and using a calculator to double check, I did buy the jar of 12 as it was the cheaper option.
#UKMathsChat
December 21, 2025 at 9:50 PM
Buying hot dogs today. The prices per 100g on the signs are a bit blurred, they were 27.7p per 100g for the jar of 12 and 43.4p per 100g for the jar of 6.
After staring at them for some time, and using a calculator to double check, I did buy the jar of 12 as it was the cheaper option.
#UKMathsChat
After staring at them for some time, and using a calculator to double check, I did buy the jar of 12 as it was the cheaper option.
#UKMathsChat
Has anyone experimented with scoring points in SET?
Playing with people of different experience levels and thinking about how to slow down the quicker players to give the others a chance to build that experience.
How about scoring a set by 1pt for every attribute that differs?
#UKMathsChat #mtbos
Playing with people of different experience levels and thinking about how to slow down the quicker players to give the others a chance to build that experience.
How about scoring a set by 1pt for every attribute that differs?
#UKMathsChat #mtbos
December 21, 2025 at 10:04 AM
Has anyone experimented with scoring points in SET?
Playing with people of different experience levels and thinking about how to slow down the quicker players to give the others a chance to build that experience.
How about scoring a set by 1pt for every attribute that differs?
#UKMathsChat #mtbos
Playing with people of different experience levels and thinking about how to slow down the quicker players to give the others a chance to build that experience.
How about scoring a set by 1pt for every attribute that differs?
#UKMathsChat #mtbos
Should've taken a picture of the Christmas tree this morning. Then I could've made a real-life version of that "Xmas - Ymas - Zmas" joke.
December 18, 2025 at 5:15 PM
Should've taken a picture of the Christmas tree this morning. Then I could've made a real-life version of that "Xmas - Ymas - Zmas" joke.
Hogfather is 99p as an ebook at the moment.
The publisher must've heard about @teakayb.mathsy.space 's readalong.
The publisher must've heard about @teakayb.mathsy.space 's readalong.
December 14, 2025 at 6:00 PM
Hogfather is 99p as an ebook at the moment.
The publisher must've heard about @teakayb.mathsy.space 's readalong.
The publisher must've heard about @teakayb.mathsy.space 's readalong.
Waterstones in Oxford has recently moved across town (nearer the Westgate, further from Blackwell's - which they now own).
Some things didn't change in the move. They still stock Good Books.
Strong recommend for Christmas.
Some things didn't change in the move. They still stock Good Books.
Strong recommend for Christmas.
December 14, 2025 at 5:37 PM
Waterstones in Oxford has recently moved across town (nearer the Westgate, further from Blackwell's - which they now own).
Some things didn't change in the move. They still stock Good Books.
Strong recommend for Christmas.
Some things didn't change in the move. They still stock Good Books.
Strong recommend for Christmas.
Reposted by Andrew Stacey
New blog post about the history of my collection of geometric visualisation puzzles Jenga Views. BONUS: I've added even more puzzles! cc @joeldavidhamkins.bsky.social davidkbutler.xyz/2025/12/11/j...
Jenga Views
This blog post is about a sequence of visual perception and geometry puzzles I have created called Jenga Views. You can download a file here with 39 puzzles, roughly in order of difficulty. In my p…
davidkbutler.xyz
December 10, 2025 at 9:56 PM
New blog post about the history of my collection of geometric visualisation puzzles Jenga Views. BONUS: I've added even more puzzles! cc @joeldavidhamkins.bsky.social davidkbutler.xyz/2025/12/11/j...
Reposted by Andrew Stacey
New blog post for maths teachers: "Things I assumed you knew"
www.resourceaholic.com/2025/12/thin...
Comments welcome!
#ukmathschat
www.resourceaholic.com/2025/12/thin...
Comments welcome!
#ukmathschat
December 7, 2025 at 1:14 PM
New blog post for maths teachers: "Things I assumed you knew"
www.resourceaholic.com/2025/12/thin...
Comments welcome!
#ukmathschat
www.resourceaholic.com/2025/12/thin...
Comments welcome!
#ukmathschat
It seems there are a few copies in the Battersea Power Station book shop, but if you want a signed copy you'll have to order one from me!¹ I have some available, but it's getting mighty close to Christmas, as far as postage is concerned.
Drop me a line if you'd like a signed copy of The Mathematicians' Library for £25 (+ £5 p&p in the UK, unless you can pick it up from Milton Keynes!)
A big, chunky hardback book with glossy pages and full-colour pictures throughout: a perfect gift for the slightly nerdy bookworm in your life!
A big, chunky hardback book with glossy pages and full-colour pictures throughout: a perfect gift for the slightly nerdy bookworm in your life!
December 3, 2025 at 7:14 AM
Reposted by Andrew Stacey
It is an acceptable risk that some people who don’t “deserve” it accidentally get help, if it means everyone who needs it is guaranteed to get help.
December 3, 2025 at 12:06 AM
It is an acceptable risk that some people who don’t “deserve” it accidentally get help, if it means everyone who needs it is guaranteed to get help.
@catrionaagg.bsky.social the image didn't show in preview
December 2, 2025 at 9:15 PM
@catrionaagg.bsky.social the image didn't show in preview
Half my y12 furthers were out today, so I threw a @catrionaagg.bsky.social problem at them and thoroughly enjoyed the next hour!
They got the answer, modulo some numbers and by using trig. So next challenge is to remove the trig.
#MathsToday #ALevelMaths #UKMathsChat
They got the answer, modulo some numbers and by using trig. So next challenge is to remove the trig.
#MathsToday #ALevelMaths #UKMathsChat
December 2, 2025 at 8:28 PM
Half my y12 furthers were out today, so I threw a @catrionaagg.bsky.social problem at them and thoroughly enjoyed the next hour!
They got the answer, modulo some numbers and by using trig. So next challenge is to remove the trig.
#MathsToday #ALevelMaths #UKMathsChat
They got the answer, modulo some numbers and by using trig. So next challenge is to remove the trig.
#MathsToday #ALevelMaths #UKMathsChat
For the second time today, my initial attempt at coding something has worked without me needing to muck about with it to fix, for example, an off-by-one error.
I'm not sure in what universe I've found myself, but it ain't the one I usually inhabit!
I'm not sure in what universe I've found myself, but it ain't the one I usually inhabit!
December 1, 2025 at 9:31 PM
For the second time today, my initial attempt at coding something has worked without me needing to muck about with it to fix, for example, an off-by-one error.
I'm not sure in what universe I've found myself, but it ain't the one I usually inhabit!
I'm not sure in what universe I've found myself, but it ain't the one I usually inhabit!
I, er, um, well, kinda, sort of, ...
In short, I haven't fully processed the existence of this yet. But I thought you should all know about it anyway.
www.bbc.co.uk/news/article...
#mathsky #ALevelMaths #UKMathsChat
In short, I haven't fully processed the existence of this yet. But I thought you should all know about it anyway.
www.bbc.co.uk/news/article...
#mathsky #ALevelMaths #UKMathsChat
What is the fast growing e-sport of competitive Microsoft Excel?
Two co-founders behind the competitive Excel UK chapter explain how the game works.
www.bbc.co.uk
December 1, 2025 at 6:57 PM
I, er, um, well, kinda, sort of, ...
In short, I haven't fully processed the existence of this yet. But I thought you should all know about it anyway.
www.bbc.co.uk/news/article...
#mathsky #ALevelMaths #UKMathsChat
In short, I haven't fully processed the existence of this yet. But I thought you should all know about it anyway.
www.bbc.co.uk/news/article...
#mathsky #ALevelMaths #UKMathsChat
Reposted by Andrew Stacey
I tried something different to help an #ALevelMaths student who was stuck with a question: instead of telling them what to do, I wrote down my thoughts about how I would solve a question (kind of like @davidkbutler.bsky.social does with #TryMathsLive, except I never actually did the question).
![I'm going to try and type you my thoughts live so you can see what I'm thinking. I hope this will be more useful to getting you started than a worked solution. I don't have a calculator on me so I haven't actually tried to work any of this out - it's possible that my approach to a particular part doesn't work! But the 'show that' in part (iii) is a nice way for you to check whether things are going well up to that point. I'd advise you to only read a bit at a time, then try what you can, and come back to read the next bit if you get stuck.
Before part (i), they've mentioned mass, speed, force and power. In particular, seeing speed and power mentioned together always makes me want to use the formula P=Fv. Given that this part is only 2 marks, I suspect I won't have to do much more than that.
Before part (ii), they've mentioned moving under gravity - given that I'm primed by part (i) that this is a Work/Energy/Power question [yes, I know this is a whole W/E/P assignment, but in an exam I wouldn't have that extra context - but even exam questions are often predominantly drawn from a single topic] that makes me think of GPE. They also mention moving against resistance, which makes me think of WD = Fd.
So already I'm thinking I'll start by trying to set up the energy buckets for the car at P and Q. I'm told the height and speed at each of them, which means I can calculate GPE and KE using the mass from the first part. I'm also told how far the car travels, which I can use as d in WD=Fd.
In fact, part (ii) only asks for GPE and KE, so I don't need to use WD=Fd at all.](https://cdn.bsky.app/img/feed_thumbnail/plain/did:plc:tdrrhbjupu4ddebjnqi57lck/bafkreic4xngzl7w5p7xu32s5iymtasz7vcstsze6lthsahdpkqif2faakm@jpeg)
December 1, 2025 at 3:38 PM
I tried something different to help an #ALevelMaths student who was stuck with a question: instead of telling them what to do, I wrote down my thoughts about how I would solve a question (kind of like @davidkbutler.bsky.social does with #TryMathsLive, except I never actually did the question).
Turns out advent only has twelve days - feel like there was another option there, but I just can't think of it.
Anyway, might actually get somewhere this year!
#AdventOfCode2025
Anyway, might actually get somewhere this year!
#AdventOfCode2025
December 1, 2025 at 6:10 PM
Turns out advent only has twelve days - feel like there was another option there, but I just can't think of it.
Anyway, might actually get somewhere this year!
#AdventOfCode2025
Anyway, might actually get somewhere this year!
#AdventOfCode2025
'Ti's the season, as they say! Ask, and ye shall receive.
November 29, 2025 at 11:25 PM
'Ti's the season, as they say! Ask, and ye shall receive.
Does anyone know of a Christmas-themed activity on loci in the complex plane?
Bit niche, I know, but surely *someone* has made one.
#ALevelMaths #UKMathsChat
Bit niche, I know, but surely *someone* has made one.
#ALevelMaths #UKMathsChat
November 28, 2025 at 10:30 PM
Does anyone know of a Christmas-themed activity on loci in the complex plane?
Bit niche, I know, but surely *someone* has made one.
#ALevelMaths #UKMathsChat
Bit niche, I know, but surely *someone* has made one.
#ALevelMaths #UKMathsChat
Reposting for the early morning g crew.
And I've just spotted the autocorrect for "cosines". Got to get that into my teaching.
#UKMathsChat #mathsky #MathsToday
And I've just spotted the autocorrect for "cosines". Got to get that into my teaching.
#UKMathsChat #mathsky #MathsToday
I decided not to read the replies until I had had a go myself. I think it's very hard to avoid the "but I know what the answer us" trap.
Here's what I tried. I started with x=tan(u), since that works if we remove the square root. That ended up with sec(u).
#MathsToday #mathsky #ALevelMaths
Here's what I tried. I started with x=tan(u), since that works if we remove the square root. That ended up with sec(u).
#MathsToday #mathsky #ALevelMaths
In #MathsToday a student asked about integrating 1/sqrt(1+x²). We haven't covered hyperbolics yet, but that got me pondering - there is a non-hyperbolic answer, so is there a route to it that doesn't go via hyperbolics?
#UKMathsChat #ALevelMaths #ITeachMaths
#UKMathsChat #ALevelMaths #ITeachMaths
November 28, 2025 at 6:16 AM
Reposting for the early morning g crew.
And I've just spotted the autocorrect for "cosines". Got to get that into my teaching.
#UKMathsChat #mathsky #MathsToday
And I've just spotted the autocorrect for "cosines". Got to get that into my teaching.
#UKMathsChat #mathsky #MathsToday
I decided not to read the replies until I had had a go myself. I think it's very hard to avoid the "but I know what the answer us" trap.
Here's what I tried. I started with x=tan(u), since that works if we remove the square root. That ended up with sec(u).
#MathsToday #mathsky #ALevelMaths
Here's what I tried. I started with x=tan(u), since that works if we remove the square root. That ended up with sec(u).
#MathsToday #mathsky #ALevelMaths
In #MathsToday a student asked about integrating 1/sqrt(1+x²). We haven't covered hyperbolics yet, but that got me pondering - there is a non-hyperbolic answer, so is there a route to it that doesn't go via hyperbolics?
#UKMathsChat #ALevelMaths #ITeachMaths
#UKMathsChat #ALevelMaths #ITeachMaths
November 27, 2025 at 10:44 PM
I decided not to read the replies until I had had a go myself. I think it's very hard to avoid the "but I know what the answer us" trap.
Here's what I tried. I started with x=tan(u), since that works if we remove the square root. That ended up with sec(u).
#MathsToday #mathsky #ALevelMaths
Here's what I tried. I started with x=tan(u), since that works if we remove the square root. That ended up with sec(u).
#MathsToday #mathsky #ALevelMaths
New visual aid for algebraic topology just dropped.
Connected#Sum #mathsky #UKMathsChat #HoagieHomies
Connected#Sum #mathsky #UKMathsChat #HoagieHomies
Porter’s Perfection set heavy clusters of fruit and in the early weeks after bloom the stems and base of the hypanthium of fruitlets that are close together can physically fuse The resulting mature apple is therefore a compound apple with a lobulated shape due to unequal growth of the fused parts
November 27, 2025 at 7:03 AM
New visual aid for algebraic topology just dropped.
Connected#Sum #mathsky #UKMathsChat #HoagieHomies
Connected#Sum #mathsky #UKMathsChat #HoagieHomies
Reposted by Andrew Stacey
I think it's time to post this again (since the thresholds have been frozen).
www.geogebra.org/m/p97htgc3
[please note this for INCOME TAX only]
www.geogebra.org/m/p97htgc3
[please note this for INCOME TAX only]
It's almost a new tax year. Here's my visualisation of how income tax works (or did in 2023-24).
Explainer vid: youtu.be/zXJCyffu8Og
Interactive version: www.geogebra.org/m/p97htgc3
Explainer vid: youtu.be/zXJCyffu8Og
Interactive version: www.geogebra.org/m/p97htgc3
November 26, 2025 at 4:18 PM
I think it's time to post this again (since the thresholds have been frozen).
www.geogebra.org/m/p97htgc3
[please note this for INCOME TAX only]
www.geogebra.org/m/p97htgc3
[please note this for INCOME TAX only]
In #MathsToday a student asked about integrating 1/sqrt(1+x²). We haven't covered hyperbolics yet, but that got me pondering - there is a non-hyperbolic answer, so is there a route to it that doesn't go via hyperbolics?
#UKMathsChat #ALevelMaths #ITeachMaths
#UKMathsChat #ALevelMaths #ITeachMaths
November 26, 2025 at 3:43 PM
In #MathsToday a student asked about integrating 1/sqrt(1+x²). We haven't covered hyperbolics yet, but that got me pondering - there is a non-hyperbolic answer, so is there a route to it that doesn't go via hyperbolics?
#UKMathsChat #ALevelMaths #ITeachMaths
#UKMathsChat #ALevelMaths #ITeachMaths
Reposted by Andrew Stacey
I enjoyed doing this question with Y7 #MathsToday. I need to remember to revisit this with Y8 when they start standard form - it’s exactly the way I want them to be thinking about it.
November 25, 2025 at 4:56 PM
I enjoyed doing this question with Y7 #MathsToday. I need to remember to revisit this with Y8 when they start standard form - it’s exactly the way I want them to be thinking about it.
Recommendation request: a good first (undergraduate) text in group theory.
Thanks!
#mathsky #ITeachMaths #UKMathsChat #HoagieHomies
Thanks!
#mathsky #ITeachMaths #UKMathsChat #HoagieHomies
November 23, 2025 at 9:29 PM
Recommendation request: a good first (undergraduate) text in group theory.
Thanks!
#mathsky #ITeachMaths #UKMathsChat #HoagieHomies
Thanks!
#mathsky #ITeachMaths #UKMathsChat #HoagieHomies