# subtraction (blogs) — RSS Amplifier Recent posts from the 1 feeds in the RSS Amplifier directory that cover subtraction. Page: Feed: --- ## [A New Fractal Construction](https://www.sineofthetimes.org/a-new-fractal-construction/) _2026-07-21 · Daniel Scher · Sine of the Times_ Several weeks ago, I saw an online post from Matt Henderson describing a fractal construction that was new to me. Here is how to generate it: Start with a hexagon and a random point A inside it. Pick a side of the hexagon at random (for example, side GH below) and construct ∆AGH. Continue by... The post A New Fractal Construction first appeared on Sine of the Times . ## [Catching the Vibe](https://www.sineofthetimes.org/catching-the-vibe/) _2026-03-21 · Daniel Scher · Sine of the Times_ This is hard to say, but I feel so…unfaithful. For 35 years, Sketchpad has been my tool of choice for designing interactive mathematical models. I’ve toyed with learning programming languages like Python, p5.js, and Snap, but a lack of motivation always got in my way. Why, I thought, spend months developing new coding skills when... The post Catching the Vibe first appeared on Sine of the Times . ## [Building with Pattern Blocks](https://www.sineofthetimes.org/building-with-pattern-blocks/) _2026-03-10 · Daniel Scher · Sine of the Times_ The websketch below (and here) provides tools to build six different pattern block shapes. To add a new pattern block to your design, tap its icon. A preview of the pattern block appears with one vertex glowing. Tap to place the pattern block in your design. You can then drag the pattern block wherever you... The post Building with Pattern Blocks first appeared on Sine of the Times . ## [Adding and Subtracting on an Open Number Line](https://www.sineofthetimes.org/adding-and-subtracting-on-an-open-number-line/) _2026-03-03 · Daniel Scher · Sine of the Times_ For some time now, Scott and I have been thinking about how we might create a Web Sketchpad model of an open number line that could offer functionality not found in the typical hand-drawn variety. We’re finally ready to share our work. Below \[and here\] is our Web Sketchpad open number line. This video explains... The post Adding and Subtracting on an Open Number Line first appeared on Sine of the… ## [Exploring a Perimeter-Area Relationship](https://www.sineofthetimes.org/exploring-a-perimeter-area-relationship/) _2026-02-19 · Daniel Scher · Sine of the Times_ Great news statistics fans: A version 3 beta of the Common Online Data Analysis Platform (CODAP) is now available. To quote the CODAP website, “\[The new CODAP\] is a powerhouse under the hood, handling much larger datasets, drawing graphs and maps faster, animating more smoothly, and responding instantly.” CODAP is the successor to Fathom, both... The post Exploring a Perimeter-Area Relationship… ## [Drawing Conic Sections Point by Point](https://www.sineofthetimes.org/drawing-conic-sections-point-by-point/) _2025-12-11 · Daniel Scher · Sine of the Times_ In my numerous blog posts about Exploring Conic Sections with The Geometer’s Sketchpad, I’ve featured an assortment of hands-on and virtual models for drawing conic sections, ranging from pins and string to paper folding to 17th-century linkages. But in order for students to understand why any of these approaches work, they must first grapple with... The post Drawing Conic Sections Point by Point… ## [Modeling with Dynamic Algebra Tiles](https://www.sineofthetimes.org/modeling-with-dynamic-algebra-tiles/) _2025-12-06 · Daniel Scher · Sine of the Times_ In this lesson, one of my favorites from Exploring Algebra 1 with The Geometer’s Sketchpad, students model expressions with dynamic algebra tiles, using the areas of the tiles to see the equivalence of expressions in factored and expanded form. Down below (and here) is a Web Sketchpad model of algebra tiles. To model (x +... The post Modeling with Dynamic Algebra Tiles first appeared on Sine of… ## [Introducing Algebra Mazes](https://www.sineofthetimes.org/introducing-algebra-mazes/) _2025-11-29 · Daniel Scher · Sine of the Times_ Welcome to Algebra Mazes, my new early algebra puzzle that shares DNA with my earlier creation, Sneaky Sums. Both Algebra Mazes and Sneaky Sums puzzles present you with a grid of shapes. Each shape represents a secret numerical value for you to deduce. Whereas Sneaky Sums puzzles were generated randomly, Algebra Mazes are handcrafted and... The post Introducing Algebra Mazes first appeared on Sine… ## [A Beautiful Application of Shearing](https://www.sineofthetimes.org/a-beautiful-application-of-shearing/) _2025-09-02 · Daniel Scher · Sine of the Times_ I must admit that I am addicted to triangle shearing problems. I’ve written about them before, and will be revisiting them soon in my City College geometry class. I mention this because several weeks ago, I encountered a problem in the LinkedIn feed of mathematics educator James Tanton that made me wonder whether a shearing... The post A Beautiful Application of Shearing first appeared on Sine of… ## [8.1% APY Plus Free Stock (Sponsored)](https://crawlproof.com/a/W4Tp81qbskUY) _2025-09-02 · **Sponsored**_ Claim 8.1% APY and up to $1,030 in SK hynix and Nvidia stock. ## [Adventures of the Scooting Tick Mark](https://www.sineofthetimes.org/adventures-of-the-scooting-tick-mark/) _2025-08-28 · Daniel Scher · Sine of the Times_ I was doing some spring cleaning a few weeks ago and came across a stash of old files that were “extra” ideas that never made their way into our Dynamic Number curriculum project. One concept in particular caught my attention—a “scooting” tick mark. Unlike traditional tick marks that dutifully sit in place on a number... The post Adventures of the Scooting Tick Mark first appeared on Sine of the…