iiinova — where your digital self keeps evolving

Tim Corica @tcorica.bsky.social · 05/10/2026

4 1/2 - 1 1/2 would be 3, but it's 1/8 less than that (5/8 - 1/2 = 1/8), so 2 7/8

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Tim Corica @tcorica.bsky.social · 04/10/2026

Very nice! Could work well with kids, too.

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Tim Corica @tcorica.bsky.social · 04/10/2026

2D Rotation matrix www.desmos.com/calculator/8...

desmos.com

RotationMatrix

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Tim Corica @tcorica.bsky.social · 04/10/2026

People are reporting that checks have arrived, with a propaganda letter blaming Biden and praising dear leader. It’s no different than the ad: political propaganda paid for by tax dollars. This was posted by another person (not mine).

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Tim Corica @tcorica.bsky.social · 30/09/2026

Oh, was about to comment here, but I see I did already, a couple of years ago!

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Tim Corica @tcorica.bsky.social · 30/09/2026

If all the dogs in the world were laid end to end…..

Tim Corica @tcorica.bsky.social · 29/09/2026

I just got it on the Web version, 11:55am ET 9/29

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Wow! New to me and very cool. I'm not sure how 90 gives "no shadow" vs "zero shadow". Wait - oh I see: "The vertical shadow cast onto a vertical wall or surface by a *horizontal* gnomon attached to that wall. This is mathematically equivalent to the tangent function." Fascinating!

I'm not sure about any of them really being lengths - I'll have to give it some thought. All three are *ratios*. Sin() and cos() are only read directly as lengths because the circle has unit radius. Tan() as slope feels right to me since both are ratios. But I'll have to think about it.

I really like tan as slope (gradient) bc it gives us tan x = tan (θ +180°) right away and also reveals the asymptotes when θ =90°, 270°.

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After they've got this (it isn't hard) I tell them that some people have a mnemonic (All Students Take Calculus or some such). If I've done my work right, they say "Why would anyone bother with a mnemonic? It's kind of obvious!" 2/2

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Yes, same here. Each point on the unit circle has coords (cos θ, sin θ), so we just need to consider the quadrant (and know that tan=sin/cos). 1/2

Be you, all the way through!

Larson's Calculus (p103 of 5th ed.) puts it clearly. The notation "= ∞" is just a convenient way to describe the behavior.

I would always say "the limit doesn't exist because values go to infinity". I do think it's important for Ss to understand that when a function increases without bound, the limit does not exist, but we describe the situation as "infinity". Infinity is *not* a limit. 2/2

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I get the desire for a definitive ans. I taught AB/BC for many years and never found one. I don't think this had any impact on the exam. CB abhors ambiguity and will, I feel certain, avoid testing things like this. Use what makes sense to you and sleep well. 1/2

limit 1 over x square as x goes to zero equals DNE or infinity?

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I found this in the course description document, p41.

Tim Corica @tcorica.bsky.social · 26/09/2026

I do pretty much the same. So for the compound inequality, we automatically translate it to "x is...." but for the single, "5 < x", it's irritating to do the translation when it could have been written "x > 5". I'd observe, though, that most people (me included) don't like this: "5 > x > 3".

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Tim Corica @tcorica.bsky.social · 26/09/2026

“more than it should “ - I get it! How do you read “5 < x < 10”? Why does this feel ok, but “5 < x” does not?

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Tim Corica @tcorica.bsky.social · 24/09/2026

And, any triangle is an equilateral triangle if you view it from the right perspective! I had a right triangle of sunlight on my screen door which cast an equilateral triangle of light on the floor, and (almost) built an MVC exercise around this. (Sadly, I can't find the photo atm.)

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Tim Corica @tcorica.bsky.social · 23/09/2026

4. This might be a good time to find/share an article about the UN recently (9/4/2026) adopting a map to replace Mercator. If you are up for it, it can lead to discussion of colonialism, western-centric thinking, and the fact that the U.S. was the only country to vote "no" on the change. Nice! 3/3

Tim Corica @tcorica.bsky.social · 23/09/2026

2. Other Ss will see your delight and praise. They will feel encouraged/emboldened to share their curiosities with you and with the class. 3. The Youtuber, by talking about a topic of relevance to MVC, implicitly lends credibilty to MVC as is important to understanding the world." 2/3

Tim Corica @tcorica.bsky.social · 23/09/2026

This is exactly the right approach! Kudos! 1. You take immediate advantage of a student's curiosity. Don't hold the problem until there's some perfect fit for a specific topic. It's perfect *now* because it's arisen *now*. 1/3

Tim Corica @tcorica.bsky.social · 22/09/2026

And once we have gotten all of these deadbeats who haven’t filed a claim off the rolls, we will have saved American taxpayers (checks notes) zero dollars.

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Tim Corica @tcorica.bsky.social · 22/09/2026

Imagine you’re a US citizen and you’re hearing this…

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Tim Corica @tcorica.bsky.social · 18/09/2026

Taught multi in hs for 15 years. Watching!

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Tim Corica @tcorica.bsky.social · 14/09/2026

30+30 is 60 7+8 is 15 60+15 is 75 Thanks, Grace!

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Tim Corica @tcorica.bsky.social · 14/09/2026

B. 70 y.o recently retired, but I’ve been B as long as I can remember.

Tim Corica @tcorica.bsky.social · 12/09/2026

Graph theorists saw this coming. They were the first to connect the dots.

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Reposted by Tim Corica

kmbailey59.bsky.social @kmbailey59.bsky.social · 11/09/2026

2026 Q1 viewership for Jimmy Kimmel Live! was 2.53 million. The Talarico interview currently has 2.9 million views. Good job stopping people from seeing it, FCC.

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Tim Corica @tcorica.bsky.social · 06/09/2026

Yes - again a little class time given to this story will reap huge benefits. #iTeachMath. #MathsToday

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Making sense of the abstract.

I could imagine, with 5 minutes left in a class period, where I've somehow run out of intentional work to do, having kids as a group do these for fun. But I'd rather have puzzles that have a longer runway, like MathForLove or www.fractalkitty.com, for example.

fractalkitty.com

Fractal Kitty

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I mean, decagons are interesting, but you don't really see them in real life. ;) #MTBOS, #MathsToday #iTeachMath

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I shared a 3D print Sugihara cylinder illusion with my 9 year old grandson last week and he was so excited to bring it home to his dad and show him. When he got there, he didn't have a good sense of how to illustrate the effect, so it fell a little flat. Having a frame like this would have done it!

*If I Were Still Teaching: I retired last year, but I still think about what I'd do with things like this!

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UN to vote on adopting new world map that shows Africa’s true scale

IIWST*: I would take time out of my math class today to share this article and explore the math and non-math concepts and ideas it would spawn. Math in the news is always worth the time. #MathsToday #iTeachMath #MTBOS www.theguardian.com/world/2026/s...

theguardian.com

Togo-sponsored resolution calls to phase out traditional map that depicts continent as similar size to Greenland

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Tim Corica @tcorica.bsky.social · 03/09/2026

No, it’s not. It give the patina of accountability without any real substance. On the ground, and in the minds of ICE agents, nothing has changed.

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Tim Corica @tcorica.bsky.social · 03/09/2026

I watched two exceptional 5th graders have a vigorous philosophical discussion about whether two labeled triangles were “the same” if one was a reflection of the other, rather than a rotation (which they agreed was the same).

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Tim Corica @tcorica.bsky.social · 01/09/2026

Is the angle computed as the traditional circular angle, or as the arc length around you wiggly curve? How does this alter the graph?

Tim Corica @tcorica.bsky.social · 31/08/2026

Nice! It seems like one could create a knights-distance geometry similarly to taxicab geometry. For example, here's what a quarter of a circle of radius 5 looks like.