---
title: "x²+y²+z²≤r²"
description: "x²+y²+z²≤r², 2026: the formula for a solid ball becomes a sphere and its cast shadow, painted on an acid-yellow square."
canonical: https://arthurfouray.systems/rt4a-2606-0201
type: CreativeWork
year: 2026
updated: "2026-10-03T21:25:14.094Z"
image: https://freight.cargo.site/w/2000/h/2000/q/75/i/K3162014024322427959712055035307/RT4A-2606-0201.jpg
license: https://creativecommons.org/licenses/by-nc-nd/4.0/
---
# x²+y²+z²≤r²

## x²+y²+z²≤r²

![x²+y²+z²≤r² 2026 Acrylic, charcoal pencil and pastel pencil on cotton canvas with gummed kraft tape 46 x 46 x 2 cm RT4A-2606-0201 Courtesy of the Artist](https://freight.cargo.site/w/2000/h/2000/q/75/i/K3162014024322427959712055035307/RT4A-2606-0201.jpg)

[**x²+y²+z²≤r²**](https://arthurfouray.systems/rt4a-2606-0201)

2026  
Acrylic, charcoal pencil and pastel pencil on cotton canvas with gummed kraft tape  
46 x 46 x 2 cm  
RT4A-2606-0201  
Courtesy of the artist

x² + y² + z² ≤ r² describes a solid ball: all points at a distance of at most r from its centre. The painting gives the formula a body—a sphere and its cast shadow on acid yellow—on the series’ square canvas.


## Structured data

```json
{
 "@context": "https://schema.org",
 "@graph": [
  {
   "@type": "BreadcrumbList",
   "@id": "https://arthurfouray.systems/rt4a-2606-0201#breadcrumb",
   "itemListElement": [
    {
     "@type": "ListItem",
     "position": 1,
     "name": "Arthur Fouray Systems",
     "item": "https://arthurfouray.systems/"
    },
    {
     "@type": "ListItem",
     "position": 2,
     "name": "rt4a",
     "item": "https://arthurfouray.systems/rt4a"
    },
    {
     "@type": "ListItem",
     "position": 3,
     "name": "x²+y²+z²≤r²",
     "item": "https://arthurfouray.systems/rt4a-2606-0201"
    }
   ]
  },
  {
   "@type": "CreativeWork",
   "@id": "https://arthurfouray.systems/rt4a-2606-0201#webpage",
   "url": "https://arthurfouray.systems/rt4a-2606-0201",
   "name": "x²+y²+z²≤r²",
   "description": "x²+y²+z²≤r², 2026: the formula for a solid ball becomes a sphere and its cast shadow, painted on an acid-yellow square.",
   "inLanguage": "en",
   "isPartOf": {
    "@id": "https://arthurfouray.systems/#website"
   },
   "breadcrumb": {
    "@id": "https://arthurfouray.systems/rt4a-2606-0201#breadcrumb"
   },
   "primaryImageOfPage": {
    "@id": "https://arthurfouray.systems/rt4a-2606-0201#image"
   },
   "creator": {
    "@id": "https://arthurfouray.systems/#arthur-fouray"
   },
   "license": "https://creativecommons.org/licenses/by-nc-nd/4.0/",
   "dateCreated": "2026"
  },
  {
   "@type": "ImageObject",
   "@id": "https://arthurfouray.systems/rt4a-2606-0201#image",
   "contentUrl": "https://freight.cargo.site/w/2000/h/2000/q/75/i/K3162014024322427959712055035307/RT4A-2606-0201.jpg",
   "url": "https://freight.cargo.site/w/2000/h/2000/q/75/i/K3162014024322427959712055035307/RT4A-2606-0201.jpg"
  }
 ]
}
```