Todd Feitelson
@toddf9.bsky.social
High School math teacher. Desmos Fellow.
Happy Cinco de Mayo (southern hemisphere).
@davidkbutler.bsky.social @nomadpenguin.bsky.social
*I think I make this joke every year. Does it even make sense in Australia? (Note: I'm not asking if it's funny.) Sorry to burden the only two southern hemispherians I know.
@davidkbutler.bsky.social @nomadpenguin.bsky.social
*I think I make this joke every year. Does it even make sense in Australia? (Note: I'm not asking if it's funny.) Sorry to burden the only two southern hemispherians I know.
November 5, 2025 at 1:08 PM
Happy Cinco de Mayo (southern hemisphere).
@davidkbutler.bsky.social @nomadpenguin.bsky.social
*I think I make this joke every year. Does it even make sense in Australia? (Note: I'm not asking if it's funny.) Sorry to burden the only two southern hemispherians I know.
@davidkbutler.bsky.social @nomadpenguin.bsky.social
*I think I make this joke every year. Does it even make sense in Australia? (Note: I'm not asking if it's funny.) Sorry to burden the only two southern hemispherians I know.
Any use for these anywhere by anybody? I’m glad to ship them. Please send this along to anyone who might care. #iteachmath
June 2, 2025 at 5:13 PM
Any use for these anywhere by anybody? I’m glad to ship them. Please send this along to anyone who might care. #iteachmath
How long would it take to fill the Rose Bowl with rain?
(an alternative to "folding paper in half again and again" and "penny doubled every day" problems which I've found Students to be too familiar with already.) #iteachmath
docs.google.com/document/d/1...
(an alternative to "folding paper in half again and again" and "penny doubled every day" problems which I've found Students to be too familiar with already.) #iteachmath
docs.google.com/document/d/1...
rose bowl
Suppose it starts to rain. During the first second, one drop of rain falls in the Rose Bowl. During the second second, two drops fall, then four drops during the third second, and so on, continuing ...
docs.google.com
April 10, 2025 at 1:43 PM
How long would it take to fill the Rose Bowl with rain?
(an alternative to "folding paper in half again and again" and "penny doubled every day" problems which I've found Students to be too familiar with already.) #iteachmath
docs.google.com/document/d/1...
(an alternative to "folding paper in half again and again" and "penny doubled every day" problems which I've found Students to be too familiar with already.) #iteachmath
docs.google.com/document/d/1...
For you hockey stats guys from the Washington Post. @joelbezaire.bsky.social
March 10, 2025 at 1:23 PM
For you hockey stats guys from the Washington Post. @joelbezaire.bsky.social
Gee willikers, AI is amazing and forcing me to rethink how I ask questions. Is it even possible? Here's what I think of as a semi-guided "thinking" question. Google's solution in the comments.
February 28, 2025 at 2:07 PM
Gee willikers, AI is amazing and forcing me to rethink how I ask questions. Is it even possible? Here's what I think of as a semi-guided "thinking" question. Google's solution in the comments.
I was driving home along a highway at 60 miles an hour. When I got exactly 60 miles from home I decided I would gradually slow down so that my speed was exactly my distance from home. How long did it take me to get home? What was my average speed? How long did it take to get 1 mile from home? #BTC
February 14, 2025 at 2:39 PM
I was driving home along a highway at 60 miles an hour. When I got exactly 60 miles from home I decided I would gradually slow down so that my speed was exactly my distance from home. How long did it take me to get home? What was my average speed? How long did it take to get 1 mile from home? #BTC
Annual quadratic ball toss day. Now on BlueSky!
January 18, 2025 at 4:14 AM
Annual quadratic ball toss day. Now on BlueSky!
Wondering:
f(x)=2x is a line with slope 2.
f(x)=3x is a line with slope 3.
So:
g(x)=x•x is a “line” with slope that changes with x, so it will be a curve.
But: the pattern would say that the slope at x=3 is 3, at x=4 is 4, etc. But we know that the slope at x=a is 2a.
<cont>
f(x)=2x is a line with slope 2.
f(x)=3x is a line with slope 3.
So:
g(x)=x•x is a “line” with slope that changes with x, so it will be a curve.
But: the pattern would say that the slope at x=3 is 3, at x=4 is 4, etc. But we know that the slope at x=a is 2a.
<cont>
January 13, 2025 at 9:26 AM
Wondering:
f(x)=2x is a line with slope 2.
f(x)=3x is a line with slope 3.
So:
g(x)=x•x is a “line” with slope that changes with x, so it will be a curve.
But: the pattern would say that the slope at x=3 is 3, at x=4 is 4, etc. But we know that the slope at x=a is 2a.
<cont>
f(x)=2x is a line with slope 2.
f(x)=3x is a line with slope 3.
So:
g(x)=x•x is a “line” with slope that changes with x, so it will be a curve.
But: the pattern would say that the slope at x=3 is 3, at x=4 is 4, etc. But we know that the slope at x=a is 2a.
<cont>
Ok, #IteachMath. Question: Why do we (typically) teach solving absolute value equations by "splitting it" into two equations (******=3 or ******=-3), but we teach solving square root equations by writing *******=+/- 3? By "we," I mean me, but I'm guessing many of you too. 🤔
December 5, 2024 at 5:03 PM
Ok, #IteachMath. Question: Why do we (typically) teach solving absolute value equations by "splitting it" into two equations (******=3 or ******=-3), but we teach solving square root equations by writing *******=+/- 3? By "we," I mean me, but I'm guessing many of you too. 🤔
Curious: what software do you use for mathematical typesetting? For making tests, etc. I use equatio, which is great for lots of things, but is not so great at alignment with text. Any suggestions? #iteachmath
November 9, 2023 at 12:46 PM
Curious: what software do you use for mathematical typesetting? For making tests, etc. I use equatio, which is great for lots of things, but is not so great at alignment with text. Any suggestions? #iteachmath
@davidkbutler.bsky.social students love star battle
October 19, 2023 at 6:31 PM
@davidkbutler.bsky.social students love star battle
My yearly post that graphfree.com is amazing.
GraphFree: Free Online Graphing Calculator
graphfree.com
October 12, 2023 at 2:58 PM
My yearly post that graphfree.com is amazing.
Desmos 3D is live! I’ve been looking forward to this for years.
I imported a project one of my students did a few years ago in Algebra II. It’s created by using systems of inequalities. # desmos3d
www.desmos.com/3d/d4f0d71636
I imported a project one of my students did a few years ago in Algebra II. It’s created by using systems of inequalities. # desmos3d
www.desmos.com/3d/d4f0d71636
Gutenberg Press
www.desmos.com
September 29, 2023 at 12:55 PM
Desmos 3D is live! I’ve been looking forward to this for years.
I imported a project one of my students did a few years ago in Algebra II. It’s created by using systems of inequalities. # desmos3d
www.desmos.com/3d/d4f0d71636
I imported a project one of my students did a few years ago in Algebra II. It’s created by using systems of inequalities. # desmos3d
www.desmos.com/3d/d4f0d71636
“I would say that the best thing you could do for honey bees right now is not take up beekeeping.”
Done and done.
www.nytimes.com/2023/08/19/b...
Done and done.
www.nytimes.com/2023/08/19/b...
September 26, 2023 at 2:48 PM
“I would say that the best thing you could do for honey bees right now is not take up beekeeping.”
Done and done.
www.nytimes.com/2023/08/19/b...
Done and done.
www.nytimes.com/2023/08/19/b...