Bill Shillito
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solidangles.bsky.social
Bill Shillito
@solidangles.bsky.social
Math instructor at Oglethorpe University. Views my own. Talk to me about anything combinatorial game theory related!

He/him. Pronounced SHILL-lit-toe.

Websites: https://www.solidangl.es, https://1dividedby0.com
Reposted by Bill Shillito
We are aware of an ongoing situation concerning our GitHub organization and Discord server (both of which have been deleted) and are working on resolving this as soon as possible.

In the meantime we have setup discord.gg/fGG4TFSdKh as a new home on Discord for our community, come join us there!
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discord.gg
December 26, 2025 at 8:22 AM
Had a dream last night… except the main thing of the dream was that I stayed in bed until like 4 PM.

There were other things going on too, but I think someone is trying to tell me to get more sleep. 😂
December 23, 2025 at 3:45 PM
Reposted by Bill Shillito
🙂‍↔️🫸 Calculus II exam
😎👉 Series finale
December 22, 2025 at 2:43 PM
Most underrated video game villain.
December 22, 2025 at 12:15 AM
Reposted by Bill Shillito
For today’s Advanced Topics test I wrote my own
@joeldavidhamkins.bsky.social -style question 😁
#iteachmath #MathSky
December 15, 2025 at 3:03 PM
Anyone have any idea where I can find a direct reference to the following quote? Especially in its original script? I want to verify the translation.

"Anantam api sankhyaatmakam iti budhyate. / Through numbers, even the infinite can be understood." — Madhava of Sangamagrama
December 9, 2025 at 5:42 PM
Students who take AP Statistics are 3x more likely to be able to tell the difference between correlation and causation.
December 7, 2025 at 2:55 AM
Which of these is an "A"? Why? #Grading

Image source: www.mpusd.net/apps/pages/i...
November 18, 2025 at 7:33 PM
Reposted by Bill Shillito
You kids and your six trig functions. Back in my day we had only one, and we used it for everything.
sin(θ)
sin(π/2 - θ)
sin(θ)/sin(π/2 - θ)
1/sin(θ)
1/sin(π/2 - θ)
sin(π/2 - θ)/sin(θ)
November 7, 2025 at 12:15 AM
If you'd never seen the definitions for the dot product and the cross product, how might you have invented them for yourself?

Who took two vectors, thought "I wonder how I multiply these", and came up with ... those?

I've been toying with this since yesterday and would love to hear other thoughts.
November 7, 2025 at 1:05 PM
Hey @desmos.com, any plans to have Desmos be able to choose between the math convention and the physics convention for θ and φ as a quick toggle?

I've taught both math majors and physics majors, and it would be nice to allow them to choose the convention that their field uses. 🙂
November 5, 2025 at 8:22 PM
How to graph y = cosh x:

TI-84 CE:
1. Press [Y=].
2. Press [2nd] [0] (CATALOG).
3. Press [PRGM] (C) to skip to the C functions.
4. Scroll down until you find cosh( and press [ENTER].
5. Type the rest of the expression and press [GRAPH].

@desmos.com:
1. Type y = cosh x.
October 29, 2025 at 11:53 PM
There's a part of math history that mystifies me.

We used to have a whole bunch of interesting named curves — cissoid, tractrix, strophoid, involute, pedal curve, and so on.

Now they've mostly been relegated to quaint examples in math textbooks.

Why were these relevant? And what happened to them?
October 24, 2025 at 11:45 PM
Question for anyone that teaches Calculus I. (Been asking this in a few chats.)

What's the point of having students learn about the normal line? What's it good for specifically? (And "they'll see normals again in Calculus III" doesn't count.)
October 24, 2025 at 1:04 PM
This was the exact moment I learned it's called "maths" across the pond.
October 21, 2025 at 12:00 AM
Ah yes, the four basic operations: addition, subtraction, checkmark, and multiplication.
October 11, 2025 at 9:07 PM
Cool thing I just realized about f-means!

If deg(f) < deg(g), then the f-mean of a data set is less than the g-mean.

So since f(x)=log x has "degree" 0 and g(x)=x has degree 1, the geometric mean is less than the arithmetic mean.

(I always forget which way it goes — now I'll always remember!)
October 10, 2025 at 2:40 AM
I've been thinking a lot about means recently!

Probably some combination of (1) teaching our data analysis unit in our STEM 101 course at Oglethorpe and (2) all of @howiehua.bsky.social's great posts surrounding Mean Girls Day.

I'd like to show how some of these various means are related.

🧵 [0]
October 9, 2025 at 2:23 AM
Welp, looks like my Erdős number is still infinity. 🙃

(My journal submission based on my dissertation research got outright rejected.)
October 2, 2025 at 1:29 PM
Reposted by Bill Shillito
What this thread doesn't mention: the English language contains the numerals lakh and crore for a significant percentage of its native speakers.

en.wikipedia.org/wiki/Indian_...
September 25, 2025 at 5:48 AM
Hot take:

The English language is not base ten.

It's base thousand.

Sure, we write numbers using the Hindu-Arabic digits 0 through 9, but the way our language is structured groups numbers in powers of a thousand.

If anything, we're sub-base ten.

(1/5)
September 25, 2025 at 2:21 AM
Holding class discussions on readings is HARD.

English teachers, how do y'all even do it?

I'm honestly struggling. 😕
September 11, 2025 at 2:30 AM
Student: “Babylonian numerals are kinda confusing… 60 is such a weird and unintuitive base.”

Me: “Yeah I know right? Oh hey by the way, what time does this class end?”

Student: “At 11:30.”

Me: *waits*

Multiple students: “…OHHHHHHHHHH”

#MathSky
September 5, 2025 at 4:57 PM
Today's lesson in COR 314!

Students learned how to count in Iñupiaq and write numbers using the Kaktovik numerals (as well as convert between base ten and base twenty). 🧮

Lots of discussion about how the way we're used to thinking isn't the only way to do things! 🙂
September 3, 2025 at 5:10 PM
Anyone else moving to more in-class assessments this semester due to AI concerns and not particularly thrilled about it, but not feeling like they have much of another choice? 😕
August 17, 2025 at 8:24 PM