Sigmoid Social

Karen CampeNew blog post! "Find Your (Math) People" -- about the vitally important connections we make w/other teachers. Be a buddy, find your groups, and carry on the legacy of <a href="https://mathstodon.xyz/@druinok" class="u-url mention" rel="nofollow noopener" target="_blank">@druinok</a> who left us too soon. <a href="https://mathstodon.xyz/tags/MTBoS" class="mention hashtag" rel="nofollow noopener" target="_blank">#MTBoS</a> <a href="https://mathstodon.xyz/tags/iTeachMath" class="mention hashtag" rel="nofollow noopener" target="_blank">#iTeachMath</a> <a href="https://mathstodon.xyz/tags/T3Learns" class="mention hashtag" rel="nofollow noopener" target="_blank">#T3Learns</a> <a href="https://mathstodon.xyz/tags/ForShelli" class="mention hashtag" rel="nofollow noopener" target="_blank">#ForShelli</a> <a href="https://karendcampe.wordpress.com/2025/08/05/find-your-math-people/" rel="nofollow noopener" translate="no" target="_blank">https://karendcampe.wordpress.com/2025/08/05/find-your-math-people/</a>

Cal Armstrong"The thing about mathematics is that it's more about connections, about people coming together." Francis Su at the Ross Lecture today. <a href="https://mathstodon.xyz/tags/mtbos" class="mention hashtag" rel="nofollow noopener" target="_blank">#mtbos</a> <a href="https://mathstodon.xyz/tags/mathed" class="mention hashtag" rel="nofollow noopener" target="_blank">#mathed</a>

Fractal KittyOk- yes I could go smaller, but it’s the last one - I’m at my limit - the paper is too thick to go any smaller with my current ability. <a href="https://mathstodon.xyz/tags/math" class="mention hashtag" rel="nofollow noopener" target="_blank">#math</a> <a href="https://mathstodon.xyz/tags/geometricSequence" class="mention hashtag" rel="nofollow noopener" target="_blank">#geometricSequence</a> <a href="https://mathstodon.xyz/tags/mtbos" class="mention hashtag" rel="nofollow noopener" target="_blank">#mtbos</a> <a href="https://mathstodon.xyz/tags/origami" class="mention hashtag" rel="nofollow noopener" target="_blank">#origami</a>

Fractal KittyA new inquiry post on my fractalkitty blog:<a href="https://www.fractalkitty.com/inquiries-week-3-r-and-rotate/" rel="nofollow noopener" translate="no" target="_blank">https://www.fractalkitty.com/inquiries-week-3-r-and-rotate/</a>I started making a separate site for tools as I work on this series, and hope to share more soon. For now, it is under construction. <a href="https://mathstodon.xyz/tags/mtbos" class="mention hashtag" rel="nofollow noopener" target="_blank">#mtbos</a> <a href="https://mathstodon.xyz/tags/math" class="mention hashtag" rel="nofollow noopener" target="_blank">#math</a> <a href="https://mathstodon.xyz/tags/iteachmath" class="mention hashtag" rel="nofollow noopener" target="_blank">#iteachmath</a> <a href="https://mathstodon.xyz/tags/inquiry" class="mention hashtag" rel="nofollow noopener" target="_blank">#inquiry</a> <a href="https://mathstodon.xyz/tags/interactive" class="mention hashtag" rel="nofollow noopener" target="_blank">#interactive</a>

Karen CampeHere's a real context <a href="https://mathstodon.xyz/tags/geometry" class="mention hashtag" rel="nofollow noopener" target="_blank">#geometry</a> question on area & volume.Home Depot changed the size of their heavy duty small box from last year to this year. What has been gained/lost? Why do you think so?Old box: 11" x 17" x 11" New box: 12" x 10" x 16"<a href="https://mathstodon.xyz/tags/iTeachMath" class="mention hashtag" rel="nofollow noopener" target="_blank">#iTeachMath</a> <a href="https://mathstodon.xyz/tags/MathsToday" class="mention hashtag" rel="nofollow noopener" target="_blank">#MathsToday</a> <a href="https://mathstodon.xyz/tags/MTBoS" class="mention hashtag" rel="nofollow noopener" target="_blank">#MTBoS</a> <a href="https://mathstodon.xyz/tags/ClassoomMath" class="mention hashtag" rel="nofollow noopener" target="_blank">#ClassoomMath</a> <a href="https://mathstodon.xyz/tags/MathEd" class="mention hashtag" rel="nofollow noopener" target="_blank">#MathEd</a> <a href="https://mathstodon.xyz/tags/MathsEdChat" class="mention hashtag" rel="nofollow noopener" target="_blank">#MathsEdChat</a>

Fractal KittyCodepen asked for spirals - did I miss any? (no I didn't do ulam - should I?). <a href="https://codepen.io/fractalkitty/live/MYwzROr/5517a9002126749dc03b84e2eceef51c" rel="nofollow noopener" translate="no" target="_blank">https://codepen.io/fractalkitty/live/MYwzROr/5517a9002126749dc03b84e2eceef51c</a><a href="https://mathstodon.xyz/tags/codepen" class="mention hashtag" rel="nofollow noopener" target="_blank">#codepen</a> <a href="https://mathstodon.xyz/tags/spirals" class="mention hashtag" rel="nofollow noopener" target="_blank">#spirals</a> <a href="https://mathstodon.xyz/tags/codepenchallenge" class="mention hashtag" rel="nofollow noopener" target="_blank">#codepenchallenge</a> <a href="https://mathstodon.xyz/tags/cpc" class="mention hashtag" rel="nofollow noopener" target="_blank">#cpc</a>-spirals <a href="https://mathstodon.xyz/tags/math" class="mention hashtag" rel="nofollow noopener" target="_blank">#math</a> <a href="https://mathstodon.xyz/tags/spirals" class="mention hashtag" rel="nofollow noopener" target="_blank">#spirals</a> <a href="https://mathstodon.xyz/tags/mtbos" class="mention hashtag" rel="nofollow noopener" target="_blank">#mtbos</a>

Fractal KittyDrafted a 3rd inquiry activity for D3 and D4 play with flips and rotations. I am hoping it's not to dry. I'll read through it again tomorrow. <a href="https://mathstodon.xyz/tags/mtbos" class="mention hashtag" rel="nofollow noopener" target="_blank">#mtbos</a> <a href="https://mathstodon.xyz/tags/dihedral" class="mention hashtag" rel="nofollow noopener" target="_blank">#dihedral</a> <a href="https://mathstodon.xyz/tags/grouptheory" class="mention hashtag" rel="nofollow noopener" target="_blank">#grouptheory</a> <a href="https://mathstodon.xyz/tags/iteachmath" class="mention hashtag" rel="nofollow noopener" target="_blank">#iteachmath</a>

Fractal KittyI have a new blog post for an inquiry activity on modular arithmetic with The Fibonacci Sequence. There is a musical toy for listening to patterns. I regret not drawing a pigeon for this. It may be a later addition. <a href="https://www.fractalkitty.com/inquiries-week-2-modular-fibonacci/" rel="nofollow noopener" translate="no" target="_blank">https://www.fractalkitty.com/inquiries-week-2-modular-fibonacci/</a><a href="https://mathstodon.xyz/tags/mtbos" class="mention hashtag" rel="nofollow noopener" target="_blank">#mtbos</a> <a href="https://mathstodon.xyz/tags/math" class="mention hashtag" rel="nofollow noopener" target="_blank">#math</a> <a href="https://mathstodon.xyz/tags/iteachmath" class="mention hashtag" rel="nofollow noopener" target="_blank">#iteachmath</a> <a href="https://mathstodon.xyz/tags/pigeonhole" class="mention hashtag" rel="nofollow noopener" target="_blank">#pigeonhole</a> <a href="https://mathstodon.xyz/tags/fibonadci" class="mention hashtag" rel="nofollow noopener" target="_blank">#fibonadci</a> <a href="https://mathstodon.xyz/tags/pisano" class="mention hashtag" rel="nofollow noopener" target="_blank">#pisano</a> <a href="https://mathstodon.xyz/tags/indieweb" class="mention hashtag" rel="nofollow noopener" target="_blank">#indieweb</a>

theHigherGeometerHere's a fun estimate (h/t a Lean Zulip chat server discussion): \[ \frac{69}{100} < \ln(2) < \frac{70}{100} \] How would you prove this?<a href="https://mathstodon.xyz/tags/mtbos" class="mention hashtag" rel="nofollow noopener" target="_blank">#mtbos</a>

theHigherGeometerMy student asked me how to give the formal definition of a subset of \(\mathbb{R}^3\) that is a surface-with-boundary. The example in question was \[\Sigma=\{(x,y,z) \in \mathbb{R}^3\mid f(x,y,z)=0\}\cap \left(D(0,1)\times\mathbb{R} \right)\] where it is "intuitively clear" (though not to him, since he doesn't 'think visually') that the boundary should be \[\partial \Sigma=\{(x,y,z) \in \mathbb{R}^3\mid f(x,y,z)=0\}\cap \left(S^1\times\mathbb{R} \right).\] He was worried about the definition of boundary of a subset in the topological sense not giving the correct thing, which indeed is the case: \(\Sigma\) has empty interior.I explained that one way is to think of \(V = \{(x,y,z) \in \mathbb{R}^3\mid f(x,y,z)=0\}\) as a topological space with the subspace topology, and then think of \(\Sigma\) as a subset of \(V\), and then look at its boundary this way, and then embed that back into \(\mathbb{R}^3\). But it's not obvious how one would do this given *only* \(\Sigma\subset \mathbb{R}^3\) as a subset. The other option is to do a formal manipulation \(\partial \sigma = V\cap \partial (D(0,1)\times \mathbb{R}) = V\cap (\partial D(0,1) \times \mathbb{R})\), but this requires having a definition of the original thing to start with to justify this type of calculation.<a href="https://mathstodon.xyz/tags/mtbos" class="mention hashtag" rel="nofollow noopener" target="_blank">#mtbos</a>

Fractal KittyI am starting a new series on the blog for inquiries in math. I posted the first one today:<a href="https://www.fractalkitty.com/inquiries-week-1-circle-shading/" rel="nofollow noopener" translate="no" target="_blank">https://www.fractalkitty.com/inquiries-week-1-circle-shading/</a><a href="https://mathstodon.xyz/tags/mtbos" class="mention hashtag" rel="nofollow noopener" target="_blank">#mtbos</a> <a href="https://mathstodon.xyz/tags/iteachmath" class="mention hashtag" rel="nofollow noopener" target="_blank">#iteachmath</a> <a href="https://mathstodon.xyz/tags/circles" class="mention hashtag" rel="nofollow noopener" target="_blank">#circles</a> <a href="https://mathstodon.xyz/tags/graphtheory" class="mention hashtag" rel="nofollow noopener" target="_blank">#graphtheory</a> <a href="https://mathstodon.xyz/tags/math" class="mention hashtag" rel="nofollow noopener" target="_blank">#math</a>

Karen CampeNew blog post: 239th Carnival of Mathematics! Recapping math/maths/mathEd content from April. <a href="https://mathstodon.xyz/tags/MTBoS" class="mention hashtag" rel="nofollow noopener" target="_blank">#MTBoS</a> <a href="https://mathstodon.xyz/tags/iTeachMath" class="mention hashtag" rel="nofollow noopener" target="_blank">#iTeachMath</a> <a href="https://mathstodon.xyz/tags/MathChat" class="mention hashtag" rel="nofollow noopener" target="_blank">#MathChat</a> <a href="https://mathstodon.xyz/tags/MathEd" class="mention hashtag" rel="nofollow noopener" target="_blank">#MathEd</a> <a href="https://mathstodon.xyz/tags/MathsEdChat" class="mention hashtag" rel="nofollow noopener" target="_blank">#MathsEdChat</a> <a href="https://mathstodon.xyz/tags/RecreationalMath" class="mention hashtag" rel="nofollow noopener" target="_blank">#RecreationalMath</a><a href="https://karendcampe.wordpress.com/2025/05/05/carnival-of-mathematics-239/" rel="nofollow noopener" translate="no" target="_blank">https://karendcampe.wordpress.com/2025/05/05/carnival-of-mathematics-239/</a>

theHigherGeometerThe other week Miss R (6) asked me if 0 was a number. And then after some thought declared that this made 1 be 0 and 1. I'm guessing she realised that once you know 0 is a number, it's allowed to participate in arithmetic operations. Later she told me that 0x0=0.Also, she thinks that the number below 0 —I'm trying to warm her up for negative numbers—is 00. Maybe because of baby clothes sizes (her little sister is up from 00 to 0 in the recent past). I didn't ask yet.<a href="https://mathstodon.xyz/tags/mtbos" class="mention hashtag" rel="nofollow noopener" target="_blank">#mtbos</a> <a href="https://mathstodon.xyz/tags/tmwyk" class="mention hashtag" rel="nofollow noopener" target="_blank">#tmwyk</a>

Fractal KittyI brushed up on my Desmos teacher activity builder skills in Desmos today and made a small intro to Conics. Yeet Paths (AKA conic Sections) <a href="https://student.desmos.com/join/xaz6th" rel="nofollow noopener" translate="no" target="_blank">https://student.desmos.com/join/xaz6th</a>Teacher Activity link: <a href="https://teacher.desmos.com/activitybuilder/custom/67f86620cbcb18d701967369?utm_campaign=share&utm_content=activity" rel="nofollow noopener" translate="no" target="_blank">https://teacher.desmos.com/activitybuilder/custom/67f86620cbcb18d701967369?utm_campaign=share&utm_content=activity</a><a href="https://mathstodon.xyz/tags/conicSections" class="mention hashtag" rel="nofollow noopener" target="_blank">#conicSections</a> <a href="https://mathstodon.xyz/tags/desmos" class="mention hashtag" rel="nofollow noopener" target="_blank">#desmos</a> <a href="https://mathstodon.xyz/tags/yeet" class="mention hashtag" rel="nofollow noopener" target="_blank">#yeet</a> <a href="https://mathstodon.xyz/tags/mtbos" class="mention hashtag" rel="nofollow noopener" target="_blank">#mtbos</a> <a href="https://mathstodon.xyz/tags/iteachmath" class="mention hashtag" rel="nofollow noopener" target="_blank">#iteachmath</a> <a href="https://mathstodon.xyz/tags/mathart" class="mention hashtag" rel="nofollow noopener" target="_blank">#mathart</a>

Cal ArmstrongDiscover how @PlayCraftLearn <a href="https://mathstodon.xyz/tags/Minecraft" class="mention hashtag" rel="nofollow noopener" target="_blank">#Minecraft</a> Education—a serious game rooted in youth culture—transforms the abstract world of mathematics into a concrete, engaging, and student-centered experience. Friday, May 9th at <a href="https://mathstodon.xyz/tags/oame2025" class="mention hashtag" rel="nofollow noopener" target="_blank">#oame2025</a> <a href="https://mathstodon.xyz/tags/onted" class="mention hashtag" rel="nofollow noopener" target="_blank">#onted</a> <a href="https://mathstodon.xyz/tags/mtbos" class="mention hashtag" rel="nofollow noopener" target="_blank">#mtbos</a> More info at <a href="https://www.oame2025.ca" rel="nofollow noopener" translate="no" target="_blank">https://www.oame2025.ca</a>

Karen CampeNew blog post! "Marvelous Midsegments" Go For Geometry! Episode 5. Activities exploring on all technology platforms: Desmos, GeoGebra & TI calculators. Taking the scenic route 😉 <a href="https://mathstodon.xyz/tags/geometry" class="mention hashtag" rel="nofollow noopener" target="_blank">#geometry</a> <a href="https://mathstodon.xyz/tags/MTBoS" class="mention hashtag" rel="nofollow noopener" target="_blank">#MTBoS</a> <a href="https://mathstodon.xyz/tags/iTeachMath" class="mention hashtag" rel="nofollow noopener" target="_blank">#iTeachMath</a> <a href="https://mathstodon.xyz/tags/ClassroomMath" class="mention hashtag" rel="nofollow noopener" target="_blank">#ClassroomMath</a> <a href="https://mathstodon.xyz/tags/MathEd" class="mention hashtag" rel="nofollow noopener" target="_blank">#MathEd</a> <a href="https://mathstodon.xyz/tags/MathsEdChat" class="mention hashtag" rel="nofollow noopener" target="_blank">#MathsEdChat</a><a href="https://karendcampe.wordpress.com/2025/03/16/go-for-geometry-5/" rel="nofollow noopener" translate="no" target="_blank">https://karendcampe.wordpress.com/2025/03/16/go-for-geometry-5/</a>

Karen CampeA few years back, I cut 1 radian of pie... and yes radius = 10cm = arclength = 10 cm. I'm really more of a pi/6 slice of pie girl myself! Happy <a href="https://mathstodon.xyz/tags/PiDay" class="mention hashtag" rel="nofollow noopener" target="_blank">#PiDay</a> to those who celebrate! <a href="https://mathstodon.xyz/tags/iTeachMath" class="mention hashtag" rel="nofollow noopener" target="_blank">#iTeachMath</a> <a href="https://mathstodon.xyz/tags/MTBoS" class="mention hashtag" rel="nofollow noopener" target="_blank">#MTBoS</a> <a href="https://mathstodon.xyz/tags/MathsToday" class="mention hashtag" rel="nofollow noopener" target="_blank">#MathsToday</a>

Leigh NataroA new blog post on polar functions. <a href="https://mathstodon.xyz/tags/iteachmath" class="mention hashtag" rel="nofollow noopener" target="_blank">#iteachmath</a> <a href="https://mathstodon.xyz/tags/MTBoS" class="mention hashtag" rel="nofollow noopener" target="_blank">#MTBoS</a> <a href="http://mathteacher24.blogspot.com/2025/03/polar-function-intersection.html?m=1" rel="nofollow noopener" translate="no" target="_blank">http://mathteacher24.blogspot.com/2025/03/polar-function-intersection.html?m=1</a>

Fractal Kitty<a href="https://mathstodon.xyz/tags/mathArtMarch" class="mention hashtag" rel="nofollow noopener" target="_blank">#mathArtMarch</a> <a href="https://mathstodon.xyz/tags/mathart" class="mention hashtag" rel="nofollow noopener" target="_blank">#mathart</a> <a href="https://mathstodon.xyz/tags/mtbos" class="mention hashtag" rel="nofollow noopener" target="_blank">#mtbos</a> I put all the prompts in one doodle :)<a href="https://mathstodon.xyz/@Ayliean" class="u-url mention" rel="nofollow noopener" target="_blank">@Ayliean</a> - thanks for hosting such a fun prompt list!

Donovan YoungWhat maths-based fiction books do teachers have on reading lists for secondary / high school pupils? <a href="https://mathstodon.xyz/tags/teaching" class="mention hashtag" rel="nofollow noopener" target="_blank">#teaching</a> <a href="https://mathstodon.xyz/tags/mtbos" class="mention hashtag" rel="nofollow noopener" target="_blank">#mtbos</a>

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